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o O o- o/a o/c o/s O/S o. O. O.A.S.I. O.B. O.B.E. o.c. O.C. o.d. O.D. o.e. O.F.M. o.g. O.G. O.H.M.S. O. Henry O.K. O.L. O.M. o.n.o. O.O.D. o.p. O.P. O.R. O.R.C. o.s. O.S. O.S.A. O.S.B. O.S.D. O.S.F. o.t. O.T. o' O' O'- O'Boyle O'Brien O'Brien potatoes O'Casey o'clock O'Connell O'Connor O'Connor, Sandra Day O'Day o'er O'Fallon O'Faoláin O'Flaherty O'Hara O'Hara, Scarlett O'Hare O'Higgins O'Keeffe O'Keeffe, Georgia O'Kelly O'Neill O'Neill, Eugene o'o O'Toole O & M O2O OA oaf oafish Oahu oak oak apple Oak-apple Day Oak Creek Oakdale oaked oaken oak fern Oak Forest oak gall Oakham Oak Harbor Oakland Oakland Park Oak Lawn oak leaf cluster oak-leaf cluster oak-leaf hydrangea oak leather oak-leaved geranium Oakley Oakley, Annie oakmoss Oak Park Oak Ridge oak-root rot Oaks oaktag oakum Oakville oak wilt oaky Oamaru stone O and O oanshagh OAO OAP OAPC OAPEC oar oared oarfish oarlock oars oarsman oarweed oary OAS OASDI oasis Oasis oast oast-house Oastler oat oatcake oaten oater Oates oat grass oath oatmeal oats OAU Oaxaca Ob OB ob- ob. oba Obad. Obadiah Obama Obamacare Oban Obasanjo obb. obbligato obclavate obcompressed obconic obconical obcordate obcuneate obdt obdt. obduce obduction obduracy obdurate OBE obeah O beautiful for spacious skies obeche obedience obedience training obedience trial obedient obedientiary obedient plant obeisance obelia obelisk obelize obelus obento Oberammergau Oberhausen Oberland Oberlin Oberon Oberösterreich Oberth obese obesity obesogen obesogenic obey obfuscate ob-gyn obi Obie obiit obit obiter dictum obituary obj. object object. object ball object code object complement object distance object glass objectification objectify objection objectionable objective objective case objective complement objective correlative objective danger objective genitive objective idealism objectively objective point objective prism objective relativism objective spirit objective test objectivism objectivist objectivity objectivize object language object lens objectless object lesson object linking and embedding object-oriented object-oriented programming object program object relations theory objet d'art objet de vertu objet trouvé objure objurgate obl. oblanceolate oblast oblate oblation obligate obligated obligation obligational obligational authority obligative obligato obligatory oblige obliged obligee obligement obliging obligor oblique oblique angle oblique circular cone oblique circular cylinder oblique coordinates oblique fault obliquely oblique motion oblique projection oblique sailing oblique section oblique-slip fault oblique triangle obliquity obliterate obliterated obliteration oblivescence oblivion oblivious obliviousness oblong oblongata obloquy obmutescence obnounce obnoxious obnubilate OBO oboe oboe d'amore oboe d'amour oboe da caccia oboist obol obole obolus Obote obovate obovoid obpyriform Obrecht Obregón Obrenović Obrenovich obreption OBrit obrogation obs obs. obscene obscenity obscurant obscurantism obscuration obscure obscurely obscurity obscurum per obscurius obsecrate obsequence obsequent obsequent stream obsequies obsequious obsequiousness obsequy observable observance observant observation observational observation car observation post observative observatory observe observer obsess obsessed obsession obsessive obsessive-compulsive obsessive-compulsive disorder obsessively obsidian obsidian dating obsidianite obsidional coin obsolesc. obsolesce obsolescence obsolescent obsolete obstacle obstacle course obstacle race obstet. obstetric obstetrician obstetrics obstinacy obstinate obstipation obstreperous obstruct obstruction obstructionism obstructionist obstructive obstruent obtain obtaining by deception obtect obtemper obtest obtrude obtrusion obtrusive obtund obtunded obturate obtuse obtuse angle obtuseness obtuse triangle Obuda OBulg. obumbrant obumbrate obv obverse obversion obvert obviate obvious obviously obvolute Obwalden obˈserver OC oc- Oc. oca Ocala OCAM O Canada ocarina occ. Occam Occam's razor occas. occasion occasional occasionalism occasional licence occasionally occasional table occasions occident Occident occidental Occidentalism Occidentalize occipital occipital bone occipital condyle occipital lobe occiput Occitan Occleve occlude occluded front occlusion occlusive occult occultation occult balance occulting light occultism occultist occupancy occupant occupation occupational occupational disease occupational hazard occupational medicine occupational pension occupational psychology Occupational Safety and Health Administration occupational therapy occupation franchise occupation groupings occupation layer occupied Occupied Territories occupier occupy occur occurred occurrence occurrent occur to one occy OCD OCDM ocean oceanarium oceanaut Ocean City ocean engineering ocean floor spreading oceanfront oceangoing ocean-going ocean greyhound Oceania oceanic Oceanic oceanic crust oceanicity oceanic ridge oceanic trench Oceanid ocean liner ocean marine insurance Ocean of Storms oceanog. oceanographer oceanography oceanologic oceanology ocean pout Oceanside Ocean Springs ocean sunfish Oceanus Oceanus Procellarum ocellar ocellated ocellated turkey ocellation ocellus ocelot och oche ocher ochlesis ochlocracy ochlophobia Ochoa ochone Ocho Rios Ochozath Ochozias ochratoxin ochre ochrea ochroid Ochs ocicat Ockeghem ocker Ockham Ockham, William of Ockham's razor ockodols Ocmulgee oconee-bells ocotillo OCR Ocracoke Island ocrea ocreate OCS Oct oct- oct. Oct. octa octa- octachord octad octadecanoic acid octagon octagonal octagon house octagon scale octahedral octahedrite octahedron octal octal notation octamer octamerous octameter octan octandrious octane octanedioic acid octane number octangle octangular octanoic acid Octans octant octarchy octaroon octastyle octateuch octavalent octave octave coupler Octavia Octavian Octavius octavo octavus octennial octet octillion octo- October October Revolution Octobrist octocentenary octodecillion octodecimo octofoil octogenarian octomerous octometer octonary octopod octopus octoroon octosyllabic octosyllable octothorpe octroi octuple octuplet octuplicate octyl alcohol octyl phenol ocul- ocular ocularist oculate oculist oculo- oculoauriculovertebral dysplasia oculomotor oculomotor nerve oculus od Od OD oda ODA odah odalisque Oda Nobunaga odd ODD oddball odd couple odd-even check Oddfellow Odd Fellow oddish oddity odd-job odd-jobman odd lot odd-lotter odd-man odd man out odd-man rush oddment odd number odd or even odd permutation odd-pinnate odds odds and ends odds and sods odds are, the Oddsbodikins oddside oddsmaker odds-on odd-toed ungulate odd trick ode odea Odelsting Odense Ode on a Grecian Urn Oder Oder-Neisse Line Odesa Odessa Ode to a Nightingale Ode to the West Wind Odets Odetta Odette odeum ODI Odia odic Odin Odinism Odinist odious Odisha odium Odoacer odograph odometer odonate odontalgia odontiasis odonto- odontoblast odontocete odontogeny odontoglossum odontograph odontoid odontoid process odontolite odontology odontophore odontorhynchous odor odorant odoriferous odorimetry odoriphore odorize odor of sanctity odorous odour odour of sanctity Odovacar Odra Odsbodikins ODT odyl Odysseus Odyssey Odzooks Oe OE Oë Ōe OECD oecology OECS oecumenical oecus OED oedema oedipal Oedipean Oedipus Oedipus at Colonus Oedipus complex Oedipus Rex oedometer OEEC Oehlenschläger oeil-de-boeuf oeillade OEM Oeneus oenochoe oenology oenomel Oenone oenophile oenothera OEO OER oersted Oersted Oerter OES Oesel oesophageal oesophagoscope oesophagus oestradiol oestrin oestriol oestrogen oestrone oestrous oestrous cycle oestrus oeuvre of OF of- of age of a kind of all things of a piece of a sort ofay of choice Ofcom of consequence of course off off. Offa OFFA off again, on again off-air offal Offaly off and on off and running off balance off-balance sheet reserve off base off-base offbeat offboard off-board off-brand off break off Broadway off-Broadway off-budget off-camera off-campus offcast off-center off-centre off chance off-color off colour offcut off duty off-duty Offenbach offence offend offended offender offense offenseless offensive offer Offer offer document offeree offering offering price offeror offer price offertory of few words, man of. off-glide off-grid off guard offhand off-hour Offiah office office automation office bearer office block office-block ballot office boy office girl officeholder office hours office junior Office of Civil and Defense Mobilization Office of Defense Transportation Office of Economic Opportunity Office of Price Administration Office of Technology Assessment Office of War Information office park officer officer of arms officer of the day officer of the deck officer of the guard officer of the watch office seeker official Official officialdom officialese official family officialism officiality officialize officially Official Receiver Official Referee Official Solicitor official strike officiant officiary officiate officinal officious officiously officious will offing offish off-island off-islander off key off-key off-kilter off label off-label offlap off-licence off-license off limits off-limits offline offload off-load off message off-message off-mike off of off off Broadway off-off-Broadway off one's chest, get off one's feed off one's guard off one's head off one's high horse off one's rocker off-peak off-piste off plan off-price off-pricer offprint off-putting off-ramp off-reserve off-road off-roader off-roading off-sales offscouring offscourings offscreen off season off-season offset offset lithography offshoot offshore offshore dock offshore drilling offshoreman offshoring offside offsider off-site off someone's back off someone's feet off someone's hands off-speed offspring offstage off-street off stump offtake off the air off the beam off the beaten track off-the-board off-the-books off the cuff off-the-cuff off the deep end off-the-face off the ground off the handle off the hook off-the-job off the mark off-the-peg off the rack off-the-rack off the rails off the record off-the-record off the shelf off-the-shelf off the top of one's head off the track off the wagon off the wall off-the-wall off-topic offtrack off-trail off-white Off with her head! Off with his head! off year off-year election Ofgas Ofgem Of Human Bondage Ofili of it oflag of late OFlem Oflot OFM Of Mice and Men of necessity of note of old of one's life of one's own accord OFr. OFris OFS of service to someone, be of sorts of sound mind Ofsted oft OFT Oftel often often as not oftentimes of the devil of the essence of the first water of the kind of the moment Of Time and the River of two minds, be ofuro Ofwat Og OG Ogaden ogam oganesson Ogasawara Gunto Ogasawara Jima O gauge Ogbomosho Ogburn Ogden Ogdensburg ogdoad Ogdon ogee ogee arch Ogeechee Ogen melon ogham Ogilvie ogive Oglala ogle Oglethorpe Ogma Ogmios OGO ogonek Ogooué Ogopogo Ogpu OGPU O grade ogre ogress Ogun Ogygian oh Oh OH OHAC OHC OHG ohia lehua Ohio Ohioan Ohio buckeye Ohio River Öhlenschläger Ohlin ohm Ohm Ohm's law ohmage ohmic ohmic resistance ohmmeter OHMS oho O horizon Ohře Ohrid Ohrmazd Ohtani rule ohv oi Oi OI OIC oidium oik oil Oil and water don't mix oil beetle oilbird oil burner oil cake oilcan Oil City oilcloth oil color oil-cooled oilcup Oildale oil derrick oil drum oiled oiled silk oiler oilfield oil field oilfired oilfish oilgas oil gilding oil gland oil-harden oil hardening oil-immersion objective oillet oillionaire oilman oil meal oil of catechumens oil of cloves oil of lavender oil of the sick oil of turpentine oil of vitriol oil of wintergreen oil paint oil painting oil palm oil pan oilpaper oil patch oil-plant oil rig Oil Rivers oil sand oil sands oilseed oil-seed rape oil shale oilskin oil slick oil spill oilspot glaze oilstone oil tanker oiltight oil varnish oil well oily oink oinochoe ointment Oireachtas Oise Oistrakh Oita oiticica oiticica oil OJ Ojibwa Ojibway Ojibwe Oji-Cree ojo caliente OJT OK oka Oka Okanagan Okanagan Lake okapi Okavango okay Okayama Okazaki oke Okeechobee Okeechobee Waterway Okefenokee Swamp Okeghem Oken okey-doke Okhotsk Okhotsk Plate Okie Okinawa Okinawan Okinawan Japanese Okla. Oklahoma Oklahoma! Oklahoma City Oklahoma City Bombing okle-dokle Okmulgee okonomiyaki okoume Okovango okra Okri okta Oktoberfest Okuninushi OL Ol. Olaf I Olaf II Olaf V olallieberry Öland Olathe Olav V Olbers Olbers' paradox Olcott old old Adam old age old age pension old as Adam Old Bailey Old Believer Old Bill old bird old boy old-boyism old boy network old-boy network Old British Old Bulgarian Old Castile Oldcastle Old Catholic old chap old chestnut old chum Old Church Slavonic old clothes man old college try, the Old Comedy Old Contemptibles old country old covenant Old Curiosity Shop, The Old Danish Old Dart Old Delhi Old Dominion Old Dutch olden Oldenbarneveldt Oldenburg Old English Old English pattern Old English sheepdog older old-established olde-worlde old face Old Faithful oldfangled old fart old fashioned old-fashioned old fellow Oldfield old field old-field colt Old Flemish old fogy Old Franconian Old French Old Frisian old fustic old girl old-girl network Old Glory old goat old gold old growth old guard Old Guard Old Guardism old habits die hard Oldham old hand Old Harry old hat Old High German Old Icelandic old identity oldie Old Ionic Old Iranian Old Irish Old Ironsides oldish Old Italian Old Kingdom old lady Old Lady of Threadneedle Street Old Latin old-line old-line party Old Line State Old Low Franconian Old Low German old maid old-maidish old man old man's beard old-man's-beard Old Man and the Sea, The old-man-and-woman old-man cactus Old Man of the Sea old man of the woods old master old media old mine cut old money old moon Old Nick Old Norse Old North French Old Northwest Old Norwegian Old Orchard Beach Oldowan Old Persian Old Portuguese Old Pretender Old Provençal Old Prussian Old Red Sandstone Old Ritualist old river old rose Old Russian Olds old saw Old Saxon old school old school tie Old Scratch old shoe old skool Old Slavic Old Slavonic old sledge old sod old soldier Old soldiers never die; they only fade away old soul Old South Old South Arabian Old Spanish Old Spanish Trail oldspeak old squaw old stager old stamping ground oldster Old Stoa Old Stone Age old story, an old style Old Style old sweat Old Swedish old talk Old Test. Old Testament old-time old-time dance old-timer old-timey Old Turkic Olduvai Gorge Old Welsh Old West oldwife Old Wives' summer old wives' tale old woman old-womanish Old World old-world Old World monkey oldy OLE olé ole- olea oleaceous oleaginous Olean oleander olearia oleaster oleate olecranon OLED olefiant gas olefin olefine olefin fiber olefin series oleic oleic acid oleiferous olein Olekma Olenek oleo oleo- oleograph oleomargarine oleo oil oleophilic oleoresin oleoresinous oleo strut olericulture olestra olethreutid oleum O level oleyl alcohol olfaction olfactometer olfactometry olfactory olfactory bulb olfactory lobe olfactory nerve olfactory tract OLG Olga olibanum olicook olid oligaemia oligarch oligarchic oligarchy oligo- Oligocene oligochaete oligoclase oligodendrocyte oligodontia oligogene oligomenorrhea oligomer oligomerous oligonucleotide oligopeptide oligophagous oligophrenia oligopoly oligopsony oligosaccharide oligospermia oligotrophic oligotrophy oliguria Ólimbos Olimpico Olin Olinda olingo olinguito olio Oliphant olivaceous Olivares olivary olivary body olive Olive olive-backed thrush olive branch olive brown olive crown olive drab olive family olive green olive-green olivenite olive oil Oliver Oliver Twist Olives olive shell olivette Olivia Olivier Olivier, Laurence olivine olla OLLA olla podrida oller ollie Ollie olm Olmec Olmert Olmsted Olmütz ologoan ology ololiuqui Olomouc Olongapo Olonos oloroso olpe Olsen Olson Olsztyn Olwen olykoek Olympia Olympiad Olympian Olympic Olympic Games Olympic Mountains Olympic National Park Olympic Peninsula Olympic-size Olympio Olympus Olympus, Mount Olympus Mons Olynthus om Om OM Om. OMA omadhaun Omagh Omaha omakase Oman Omani Omar Omar Khayyam Omar Khayyám omasum Omayyad OMB OMBE omber ombre ombrellino ombro- ombrogenous ombrophilous ombrophobous ombu ombudsman ombudsperson ombudswoman Omdurman omega omega-3 fatty acid omega baryon omega-c baryon omega meson omega minus omega-minus particle omelet omelette omen omentum omeprazole omer Omer omertà OMG omicron omics omigod ominous ominously omissible omission omissive omit omitted Omiya OMM ommateum ommatidium ommatophore Ommiad omn. bih. omn. hor. omn. man. omn. noct. omn. quadr. hor. omni- omnia mutantur, nos et mutamur in illis omnia vincit amor omnibearing omnibus omnibus clause omnicide omnicompetent omnidirectional omnidistance omnifarious omnific omnificent omnigraph omnipotence omnipotent omnipresent omnirange omniscience omniscient omnisexual omnishambles omnium-gatherum omnivore omnivorous Omolara Omolon Omoo omophagia omophorion omotenashi Omotic OMOV omphacite Omphale omphalos omphaloskepsis Omri OMS Omsk omurice Omuta OMW on On ON Ona on account on account of on a dime on a first-name basis on again on-again, off-again onager onagraceous on-air on a limb on all fours on and off on and on on an even keel onanism onanist onanistic on a par with on a pedestal, put on approval on a rampage on a roll on a shoestring Onassis Onassis, Jacqueline Kennedy on a string on a tangent Oñate on balance onbeat on behalf of on bended knee onboard on board onboarding ONC on call on camera on-camera once once and for all once bitten, twice shy Once bitten, twice shy once in a blue moon once in a lifetime once in a while Once more unto the breach, dear friends once-over once over lightly once-over-lightly oncer once upon a time onchocerciasis oncidium on cloud nine onco- oncogene oncogenesis oncogenic oncogenicity oncolite oncologist oncology oncoming on commission on condition that on consignment oncornavirus oncost OND Ondaatje on deck on demand ondes Martenot ondine onding on dit Ondo ondograph on draft on duty one one-a-cat one-acter one and all one and only one and the same one another one-armed bandit on earth on easy street one-bagger one-base hit one by one on edge one-dimensional one-down one-drop rule one-eighty one-eyed one eye on one fell swoop, in onefold one foot in the grave, have one for the books one for the road Onega Onega Bay one good turn deserves another One good turn deserves another Oneg Shabbat one-handed one-horse one-horse town Oneida Oneida Community Oneida Lake One if by land, and two if by sea one in a million oneiric oneiro- oneirocritic oneirocriticism oneiromancy one jump ahead one-legged one-liner one-lung one-lunger one-man one man's meat is another man's poison One man's meat is another man's poison one-man show one-many on end oneness one-nighter one-night stand one-note one of a kind one-off one of these days one of those days one old cat one on, that's one-one one on one one-on-one Oneonta one-parent family one picture is worth a thousand words one-piece oner one-reeler One rotten (or bad) apple spoils the barrel onerous oneself one-shot one-sided onesie one-size-fits-all one-spot one-star one-step one-stop one-suiter one-tailed one that loved not wisely but too well One Thousand Guineas one-time one-to-one one-track one-track mind one-trick pony Onetti one-two one up one-up one-upmanship one-way one-way mirror one way or another one-way ticket one-woman one-worlder oneˈ-upmanship on faith, take it on file on fire on foot ONFr. ongaonga on-glide ongoing ongoings on good terms on hand on high on hold ONI on ice onie onigiri on in years oniomania onion onion dome onion fly onion rings Onions onionskin onion snow onion weed Onitsha on its merits onium compound Onkelos on key onkus onlap onlay On Liberty onliest on-limits online on line online catalog online dictionary onliner online thesaurus onload onlooker onlooking only only-begotten only game in town, the only too on message on-message on-mike onnagata on no account on occasion on-off onomasiology onomastic onomasticon onomastics onomatology onomatopoeia Onondaga Onondagan on one's on one's account on one's behalf on one's best behavior on one's doorstep on one's feet on one's good behavior on one's guard on one's head on one's heels on one's high horse on one's home ground on one's honor on one's last legs on one's mind on one's own on one's own account on one's own time on one's part on one's say-so on one's shoulders on one's soapbox on one's tail on one's toes on one's uppers on one's way on one hand on oneself on order on pain of on paper on-peak on pins and needles on principle on purpose ONR on-ramp on record on-record on relief on request onrush ONS Onsager on sale on schedule on-screen on-seam on-season on second thought onset onshore onshoring onside onside kick on sight on-site onslaught Onslow on someone's on someone's back on someone's coattails on someone's nerves on someone's side on speaking terms on spec onstage on standby on-stream on strike on sufferance ont- Ont. on tap on target on-target Ontarian Ontario on tenterhooks on the air on the alert on the average on the ball, be on the bandwagon, get on the barrel on the beam on the bench on the blink on the block on the brain on the bum on the button on the carpet on the chance that on the cheap on the chin on the contrary on the cuff on the defensive on the dot on the double on the edge on the eve of on the face of it on the fence, be on the fly on the fritz on the go on the heels of on the Hill on the horizon on the horns of a dilemma on the hour on the house on the in, be on the increase on the inside on the job on-the-job on the lam on the level on the line on the lines of on the lookout on the loose on the make on the map on the mark on the market on the mend on the money on the move on the nail on the nose on the off chance on the one hand on the order of on the other foot on the other hand on the outs on the part of on the point of on the prowl on the Q.T. on the qui vive on the rack on the rebound on the receiving end on-the-record on the right foot, get off on the right tack on the road On the Road on the rocks on the ropes on the run on the safe side on the same wavelength on-the-scene on the scene, be on the shelf on the side on the sidelines on the side of the angels on the skids on the sly on the spot on-the-spot on the spur of the moment on the square on the street on the strength of on the surface on the table on the take on the tip of one's tongue on the town on the up-and-up on the uptake on the verge of on the wagon on the warpath on the watch on the way on the way out on the whole on the wing on the wrong foot on the wrong side of bed on the wrong tack on thin ice ontic on time on tiptoe onto onto- on to onto function ontogeny ontological ontological argument ontologism ontologize ontology on top on top of on top of the world on-trend on trial onus onus probandi on view onward onwards on welfare ony onychia onychophagia onychophoran onymous on your life onyx onyxis onyx marble ONZ oo- ooblast oocyst oocyte oodles oof oogamete oogamy OO gauge oogenesis oogonium ooh ookinesis Ookpik oolachan oolite oolith oology oolong oom oomiak oompah Oom Paul oomph oomycete oomycota Oona oont OOO OOP oophorectomy oophoritis oophyte oops Oort Oort cloud oory oose oosperm oosphere oospore Oost Oostende OOT ootheca ootid ooze ooze leather oozy op OP op- op. Op. op. cit. OPA opacify opacity opacus opah opal Opal opalesce opalescence opalescent opaleye opal glass opaline opalite Opa-Locka opaque opaque context opaque projector op art OPC ope OPEC Opechancanough op-ed Op-Ed Opelika Opelousas open openable open account open admissions open adoption open air open-air open and aboveboard open and shut open-and-shut open-angle glaucoma open bar open book Open Brethren open call open caption open carry open-carry open-cast opencast mining open chain open cheque open circuit open city open classroom open cluster Open College open communion open-concept open convention open couplet open court open cover open cut open-cut open-cut mining open dating open day open diapason open die open door open doors open educational resource open-end open-ended open-end mortgage open enrollment opener open-eyed open-faced open field open-field open fire open flash open fracture open frame open game openhanded open-handed open-hearted open-hearth open-hearth furnace open-hearth process open-heart surgery open house open house, keep open housing opening opening night opening time open interval open-jaw open juncture open learning open letter open-line open loop open market open-market operations open marriage open mic open mike open mind open-minded open-mouthed openness open one's eyes open one's heart to open one's mouth open order open-pit open plan open-plan open policy open-pollinated open position open primary open prison open punctuation open question open quote open-reel open-reel tape open registry open sandwich open sea open season open season on open secret open sentence open sesame open set open-shelf open shop open side open-sided open sight open slather open source open-source open space open-stack open stance open-standard open stock open string open system open texture open the door to open-timbered open trailer open union open universe Open University open up open verdict open-web open with openwork OPer. opera operable opéra bouffe opera buffa opera cloak opéra comique opera glasses operagoer opera hat opera house operand operant operant conditioning operant learning opera seria operate operatic operating operating budget operating income operating room operating system operating table operating theatre operation operational operational amplifier operational calculus operationalism operationalize Operation Barbarossa Operation Desert Storm Operation Overlord Operation Sealion operations research operations room operative operatize operator operatory opera window opercle operculate operculum opere citato operetta operon operose opgefok Ophelia Opheltes ophicleide ophidian ophidiid ophiolatry ophiolite ophiolite suite ophiology ophiophagous Ophir ophite ophitic Ophiuchus ophiuroid ophthal. ophthalm- ophthalm. ophthalmia ophthalmia neonatorum ophthalmic ophthalmic optician ophthalmitis ophthalmo- ophthalmodynamometer ophthalmol. ophthalmologist ophthalmology ophthalmometer ophthalmoscope ophthalmoscopy Ophüls opiate opiatic opine opined opinicus opinion opinionated opinionative opinioned opinion poll opioid opioid antagonist opioid epidemic opistho- opisthobranch opisthodomos opisthognathous opisthograph opisthosoma opium opium den opiumism opium poppy Opium War Opium Wars OPM Opole Oporto opossum opossum block opossum shrimp opotherapy opp. Opp. Oppenheim Oppenheimer Oppenheimer, J. Robert oppidan oppilate oppo opponency opponent opportune opportunism opportunist opportunistic opportunistically opportunistic infection opportunity opportunity cost opportunity shop opposable opposable thumb oppose opposed opposed-cylinder opposed-piston engine opposeless opposing opposite opposite field opposite number opposite number, one's opposite prompt opposite sex opposition oppositional oppositional defiant disorder oppositionist opposition research oppositive oppress oppressed oppression oppressive oppressor opprobrious opprobrium oppugn oppugnant OPRA opry Ops OPS ops. op-shop opsimath opsin opsonic opsonic index opsonify opsonin opsonize opt opt. optative opted optic Optic optical optical activity optical art optical astronomy optical bench optical binary optical center optical character reader optical character recognition optical computer optical crown optical density optical disc optical disk optical double star optical effects optical fiber optical fibre optical flint optical glass optical illusion optical isomer optical isomerism optical mark reading optical maser optical microscope optical mouse optical path optical printer optical pumping optical pyrometer optical resonator optical rotation optical scanner optical scanning optical sound optical soundtrack optical tooling optical tweezers optical wedge optic axis optic chiasma optic disc optician opticist optic nerve optics optic thalamus optimal optimally optime optimism optimist optimistic optimization optimize optimum optimum population opt in option optional optionee option money opto- optoelectronics optometer optometrist optometry optophone optotype opt out opulence opulent opuntia opus opus anglicanum opuscule opusculum Opus Dei oquassa or OR ora ORAC orach orache oracle oracle bones oracles oracular oracy orad Oradea ora et labora oral oral contraceptive orale oral eroticism oral-formulaic oral herpes oral history oral hygiene oral hygienist oral interpretation oralism oralist orality Oral Law orally oral personality oral sex oral society oral stage oral surgery oral tradition Oran orang orange Orange orangeade orange blossom Orangeburg orange chromide orange flower oil orange flower water Orange Free State orange hawkweed Orangeism orange lily Orangeman Orangeman's Day Orangemen's Day orange peel orange-peel fungus orange pekoe orange roughy orange rust orangery oranges orange stick orange-tip Orangevale Orangeville orangewood orangutan orang-utan orangy Oranian orans orant ora pro nobis orarion orarium orate orate fratres oration orator Oratorian oratorical oratorio oratory Oratory oratrix orature orb orbicular orbiculate Orbison orbit orbital orbital angular momentum orbitale orbital index orbital quantum number orbital sander orbital velocity orbiteer orbiter Orbiting Astronomical Observatory Orbiting Geophysical Observatory Orbiting Solar Observatory orb weaver orby orc orca Orcadian Orcagna orcein orch. orchard orchard bush orchard grass orchardist orchardman orchard oriole orchard valve orchectomy orchestra orchestral orchestrate orchestration orchestrina orchestrion orchi- orchid orchid- Orchidaceae orchidaceous orchidectomy orchid family orchido- orchidology orchidotomy orchid tree orchiectomy orchil orchis orchitis orchotomy orcinol OR circuit Orcus Orczy Ord ord. ordain ordained ordainee ordeal ordeal bean ordeal tree order order about order arms order bill of lading order-driven ordered ordered field ordered pair ordered set order in council ordering orderly orderly marketing agreement orderly officer orderly room Order of Australia order of battle order of business Order of Canada order of magnitude Order of Merit Order of Military Merit order of the day order of the day, the Order of the Garter Order of the Thistle order paper order port orders order someone about ordinal ordinal number ordinal numbers ordinal scale ordinance ordinand ordinariate ordinarily ordinary ordinary differential equation Ordinary grade ordinary income ordinary jubilee ordinary-language philosophy ordinary lay Ordinary level ordinary life insurance ordinary point ordinary rating ordinary ray ordinary seaman ordinary share ordinary shares ordinary stock ordinary wave ordinate ordination ordn. ordnance ordnance datum Ordnance Survey ordo Ordóñez ordonnance Ordos Ordovician ordure Ordzhonikidze ore öre Ore. oread orebody ore bridge Örebro orecchiette orectic ore dressing Oreg. oregano Oregon Oregon cedar Oregon City Oregon crab apple Oregon fir Oregon grape Oregonian Oregon myrtle Oregon pine Oregon trail Oregon Trail ore hearth oreide Orekhovo-Zuyevo Orel or else Orem Ore Mountains Orenburg orenda Orense Oreo oreodont Oreopithecus ore rotundo oreshoot Oresme Oresteia Orestes Orestes complex ore tanker orexis orf orfe Orfeo ed Euridice Orff orfray org org. organ organa organdie organdy organelle organelles organ grinder organ-grinder organic organic acid organically organic chemistry organic compounds organic disease organicism organic light-emitting diode organic molecule organic molecules organic psychosis organic solidarity organism organist organization organizational organizational culture organizationally organizational psychology organization chart Organization for Economic Cooperation and Development Organization for European Economic Cooperation organization man Organization of African Unity Organization of American States Organization of Petroleum Exporting Countries organize organized organized labor organized militia organizer organ meat organo- organ of Corti organogenesis organogram organography organoleptic organology organomagnesium organometallic organon organophosphate organosilicon organosiloxane organotherapy organotin organotropism organ pipe organ-pipe cactus organ-pipe coral organ point organ screen organum organ whistle organza organzine orgasm orgasmic orgeat Orgetorix orgiastic orgone orgone box orgone energy orgulous orgy oribi orichalcum oriel oriel window orient Orient oriental Oriental Oriental alabaster Oriental almandine oriental beetle Oriental carpet Oriental cat's eye oriental cockroach Oriental emerald Oriental fruit moth Orientalia Orientalism Orientalist Orientalize Oriental poppy Oriental rug Oriental topaz orientate orientation Oriente orienteer orienteering Orient Express orifice orifice meter oriflamme orig. origami origan origanum Origen Origenism origin original original equipment manufacturer originalism originalist originality originally original sin originate origination fee originative Origin of Species, The origin story orihon orihou Orillia orinasal Orinda O-ring Orinoco oriole Orion Orionids Orion Nebula orisha Oriskany orismology orison Orissa orixa Oriya Orizaba Orjonikidze Orkhon Orkney Orkney Islands Orlando Orland Park orle Orléanais Orleanist Orléans Orléans, d' orlfly Orlich orlo Orlon orlop Orlov Orly Ormandy Ormazd ormer ormolu Ormond Beach Ormonde Ormuz ornament ornamental ornamentalism ornamentation ornamented ornate ornately Orne ornery ornis ornith- ornith. ornithic ornithine ornithischian ornitho- ornithoid ornithol. ornithological ornithologist ornithology ornithomancy ornithophilous ornithophily ornithopod ornithopter ornithorhynchus ornithoscopy ornithosis oro oro- orobanchaceous orogen orogeny orographic cloud orographic precipitation orography oroide orometer Oromo oronasal Orono Orontes oropendola oropharynx Orosius or other orotund oro y plata Orozco Orpen orphan orphanage orphan drug orphans' court orpharion Orphean Orpheus Orpheus and Eurydice Orphic Orphism orphrey orpiment orpine Orpington Orr orra orrery Orrin orris orrisroot Orsha Orsini Orsk or so Orson ort ortanique Ortega Ortegal Ortega Saavedra Ortega y Gasset orth- orth. Orth. orthicon ortho ortho- orthoboric acid orthocenter orthocentre orthocephalic orthochromatic orthoclase orthoclastic ortho-cousin ortho-dichlorobenzene orthodontia orthodontics orthodontist orthodonture orthodox Orthodox Orthodox Christianity Orthodox Church Orthodox Jew Orthodox Judaism orthodox sleep orthodoxy orthoepy orthoformate orthoformic acid orthogenesis orthogenetic orthogenic orthognathic surgery orthognathous orthogonal orthogonalize orthogonal matrix orthogonal projection orthogonal trajectory orthographer orthographic orthographic projection orthographize orthography orthohydrogen orthokeratology orthomolecular orthomorphic orthomorphic projection orthonormal Ortho-Novum orthopaedic orthopaedics orthopedic orthopedics orthopedist orthophosphate orthophosphoric acid orthophosphorous acid orthophthalic acid orthophyric orthopnea orthopod orthopraxia orthopraxy orthopsychiatry orthopter orthopteran orthopteron orthopterous orthoptic orthoptics orthopyroxene orthorexia orthorhombic orthoscope orthoscopic orthoselection orthosis orthostat orthostates orthostatic orthostatic hypotension orthostichy orthostyle orthotic orthotics orthotist ortho-toluidine orthotone orthotropic orthotropism orthotropous ortho-xylene orthros Ortler Ortles ortolan Orton orts Orumiyeh Oruro ORV Orvieto Orville Orwell Orwell, George Orwellian or what or whatever Oryol oryx orzo orˈthoptist os Os OS OSA Osage Osage orange Osaka Osasco OSB Osbert Osborn Osborne Osborne House Oscan oscar Oscar Oscar II OSCE Osceola oscillate oscillating circuit oscillating engine oscillating universe oscillating universe theory oscillation oscillator oscillatory oscillogram oscillograph oscillometer oscilloscope oscine oscitancy oscitant Osco-Umbrian osculant oscular osculate osculating circle osculating plane osculation osculum OSD Osee Ösel Osetic OSF OSFCW Osgood Osh OSHA Oshawa Oshkosh Oshogbo Oshun OSI osier Osijek Osiris Oskaloosa Öskemen OSlav Osler Oslo Oslo Accord Oslo Fiord Osman Osman I Osmanli osmatic osmeterium osmic osmics osmidrosis osmious osmiridium osmium osmium tetroxide osmo- osmolarity osmole osmometer osmometry osmoregulation osmose osmosis osmotic osmotically osmotic pressure osmous osmund osmunda Osnabrück osnaburg OSO Osorno OSp OSP osprey OSRD OSS ossa Ossa ossature ossein osselet osseous Osset Ossetia Ossetian Ossetic Ossi ossia Ossian Ossianic ossicle Ossie Ossietzky ossiferous ossification ossified ossifrage ossify Ossining osso bucco ossobuco ossuarium ossuary OST O star oste- osteal ostectomy osteichthyan Osteichthyes osteitis osteitis deformans Ostend Ostend Manifesto ostensible ostensibly ostensive ostensive definition ostensorium ostensory ostentation ostentatious osteo- osteoarthritis osteoarthrosis osteoblast osteochondritis osteochondrosis osteoclasis osteoclast osteocope osteocyte osteofibrosis osteogenesis osteogenesis imperfecta osteogenic osteoid osteology osteoma osteomalacia osteometry osteomyelitis osteopath osteopathy osteopetrosis osteophyte osteoplastic osteoplasty osteoporosis osteoporotic osteoradionecrosis osteosarcoma osteosclerosis osteosis osteotome osteotomy Österreich Ostia ostiary ostinato ostiole ostium ostler ostmark Ostmark ostomy ostosis Ostpolitik Ostpreussen ostracism ostracization ostracize ostracod ostracoderm ostracon ostrakon ostranenie Ostrava ostrich ostrich fern Ostrogoth Ostrovsky Ostwald Ostyak Osun Oswald Oswald, Lee Harvey Oswego Oswego tea Oświęcim OT ot- OTA Otago Otaheite apple Otaheite orange otaku otalgia Otaru OTB OTC OTE Otello O tempora! O mores! Othello other other day, the other-directed other fish to fry other good fish in the sea otherguess other half otherize otherkin other man otherness other ranks other side of the coin other side of the tracks other than other things being equal other way round, the otherwhere otherwhile otherwise other woman other world otherworldly Othin Othman Othman I Othniel Otho I Othoniel otic otiose Otis otitis otitis externa otitis interna otitis media otium cum dignitate Oto oto- otocyst Otoe OTOH otolaryngologist otolaryngology otolith otology Oto-Manguean Otomi otoplasty otorhinolaryngological otorhinolaryngology otorrhea otorrhoea otosclerosis otoscope ototoxic Otranto OTS Otsu OTT ottar ottava ottava rima Ottawa otter Otter Otterbein otter board Otterburn otterhound otter hound otter shell otter shrew otter trawl otto Otto Otto cycle Otto I Otto II Otto III Otto IV ottoman Ottoman Ottoman Empire Ottonian ottrelite Ottumwa Otway ou OU ouabain Ouachita Ouachita Mountains Ouagadougou ouananiche oubaas Oubangi Oubangui oubliette ouch oud Oudh Oudry Oudtshoorn Ouémé Ouessant ought oughtlins oughtn't ouguiya oui Ouida Ouija Ouija board Oujda Oulu Oulujärvi ouma ounce ounce of prevention is worth a pound of cure, an ouncer oupa ouphe our Ouranos ourari Our Father ourie Ourinhos Our Lady ourn Ouroboros ours ourself ourselves Our Town Ouse ousel Ouspensky oust ousted ouster out out- Out, damned spot! outact outage out and about out and away out-and-out out-and-outer outargue outasight out-a-sight out at the elbows outback out back outbalance out-basket outbid outbluff outboard outboard motor outboard profile outbond outbound outbox outbrave outbreak outbreed outbreeding outbuilding outburst outcall outcast outcaste outclass outclimb out cold outcome outcompete out-country outcrop outcross outcry outcurve outdare outdate outdated outdistance outdo outdoor outdoor relief outdoors outdoorsman outdoorswoman outdoorsy outdraw outdrive outdweller outen outer outer automorphism outer bar outer barrister outercoat outercourse outer ear outer garments Outer Hebrides Outer Mongolia outermost outer planet outer product outersole outer space outerwear outface outfall outfield outfielder outfighting outfit outfit car outflank outflow outflux outfly outfoot out for, be out for the count outfox out from under out front out-front outfrown outgas outgeneral outgiving outgo outgoing outgoings out-group outgrow outgrowth outguess outgun out-half outhandle outhaul out-Herod outhit outhouse outie outing outing flannel out in left field out in the cold out in the open outjockey outlaid outland outlander outlandish outlandishly outlast outlaw outlawry outlaw strike outlay outleap outlet outlet mall outlet store outlier out like a light outline outline font outlive outlook out loud outlying outman outmaneuver outmanoeuvre outmarch outmatch out-migrant out-migrate outmode outmoded outmost outmuscle outness outnumber out of, be out of a clear blue sky out-of-body out-of-body experience out of bounds out-of-bounds out of breath out of business out of character out of circulation out of commission out of condition out of control out-of-court out of date out-of-date out-of-door out-of-doors out of fashion out of favor out of gas out of hand out of harm's way out of humor out of it out of joint out of keeping out of key out of kilter out of line out of luck out of nowhere out of one's out of one's depth out of one's element out of one's hair out of one's mind out of one's shell out of one's system out of one's way out of order out of phase out of place out of pocket out-of-pocket out of practice out of print out-of-print out of proportion out of reach out-of-round out of season out of shape out of sight out-of-sight Out of sight, out of mind out of sorts out of square out-of-state out-of-stater out of step out of stock out-of-sync out of the blue out of the corner of one's eye Out of the frying pan, into the fire out of the frying pan into the fire out of the hole out of the loop out of the mouths of babes out of the ordinary out of the picture out of the question out of the rain out of the running out of the way out-of-the-way out of the window out of the woods out of the woodwork out of thin air out of this world out of touch out of town out-of-town out-of-towner out of turn out of wedlock out of whack out of whole cloth out of work out on a limb out on bail out on one's ear out on the town outpace outparish outpatient outperform outplace outplacement outplay outpoint outport outporter outpost outpour outpouring out-process outpull output outrace outrage outrageous Outram outrance outrang outrange outrank outré outreach out-relief Outremont outride outrider outrigger outright outring outro outrow outrun outrunner outrush outs outsail outsang outsat outscore outsell outsert outset outsettlement outsettler outshine outshoot outshout outside outside broadcast outside caliper outside director outside forward outside half outside loop outside of outsider outsider art outside voice outside work outsight outsing out sister outsit outsize outskirt outskirts outsleep outsmart outsoar outsold outsole outsource outspan outspeak outspend outspent outspoken outspread outsprint outstand outstanding outstare outstation outstay outstretch outstrip outstroke outsung outswear outswing outswinger outta outtake outtalk outtell out there outthink outthrow outthrust out to lunch outtough outtrade out-tray outturn outvote outwait outwalk outward Outward Bound outward-bound outwardly outwards outwash outwash plain outwatch outwear outweigh outwent outwit outwith out with it outwork outworn outwrite outyear ouzel ouzo ov- ova oval Oval ovalbumin ovality oval kumquat Ovalle oval of Cassini Oval Office ovals of Cassini oval window Ovambo ovarian ovariectomy ovaries ovariole ovariotomy ovaritis ovarium ovary ovate ovation ovel oven ovenable ovenbird ovenproof oven-ready ovenware ovenwood over over- over a barrel overabundance overachieve overachiever overact overactive over again over against overage overaggressive overall overambitious over and above over and done with over and over overanxious overarch overarching overarm overattentive overawe overbalance overbank overbear overbearing overbid overbite overblouse overblow overblown overboard overbook overboot overbore overborne overbought overbrake overbreak overbroad overbudget overbuild overburden overburdensome overbuy overcall overcapacity overcapitalize overcareful overcast overcasting overcautious overcertify overcharge overcheck overclass overclock overclocking overclothes overcloud overcoat Overcoat, The overcoating overcoil overcome overcomer overcommit overcompensate overcompensation overcomplex overconfidence overconfident overconsumption overcook overcorrection overcritical overcrop overcrowd overcrowding overcurrent overdate overdelicate overdependence overdependent overdetermination overdetermined overdevelop overdeviate overdo overdog overdone overdoor overdose overdraft overdraft checking account overdrafting overdraught overdraw overdrawer overdress overdrive overdub overdue overdye overeager over-ear over easy overeat overegg overelaborate overemphasis overemphasize overenthusiastic overestimate overexcite overexcited overexert overexertion overexpansion overexploitation overexpose overexposure overextend overfall overfalls overfamiliar overfatigue overfeed overfill overfish overfished overflap overflight overflow overfly overfold overfond overfull overfunding overgarment overgear overgeneralization overgeneralize overgenerous overgild overglaze overgraze overground overgrow overgrown overgrowth overhand overhand knot overhang overharvest overhasty overhaul overhead overhead camshaft overhead door overhead projector overhead railway overheads overhead-valve engine overhear overheat overhit overhung Overijssel overindulge overissue overjoy overjoyed overkill overlade overlaid overland Overland overland mail Overland Park overland stage Overland Trail overlap overlarge overlay overlay glass Overlea overleaf overleap overlearn overleverage overlie overline overlive overload overlong overlook overlooked overlooker overlord overly overman overmantel overmaster overmatch overmatter overmeasure overmodulation overmorrow overmuch over my dead body overnice overnight overnight bag overnighter overnight telegram overnutrition over one's head overoptimism overoptimistic overorganize overpage overparted overpass overpay overpayment overpeople overpersuade overpitch overplay overplus overpolice overpopulate overpopulated overpopulation overpotential overpower overpowering overpraise overpressure overprice overpriced overprint overprivileged overprize overproduce overproduction overpronounce overproof overproportion overprotect overprotective overproud overqualified overquick overrake overrate overrated overreach overreact overreaction overrefine overrefinement overregulation overreliance overrepresent overrich override overrider overriding overripe overruff overrule overrun overrun brake oversaturated overscale overscore overscrupulous overseas overseas cap overseas telegram oversee overseer oversell oversensitive overset oversew oversexed overshade overshadow overshare overshine overshirt overshoe overshoot overshot overshot wheel overside oversight oversimplify oversize overskirt overslaugh oversleep oversleeve overslip oversold oversolicitous oversoul overspecialization overspend overspill overspin overspread overstaff overstand overstate overstay overstayer oversteer overstep overstimulation overstitch overstock overstood overstory overstress overstretch overstrew overstride overstrike overstring overstructured overstrung overstudy overstuff overstuffed oversubscribe oversupply overswing overt overtake overtask overtax over-the-air over the counter over-the-counter over the edge over the hill over the hump over the moon over-the-road over the top overthink overthrow overthrust overthrust belt overtime overtire overtired overtly overtone overtop overtopping overtourism overtrade overtrain overtrick overtrump overture overturn over-under overuse over-use overvalue overview overvoltage overwatch overwear overweary overween overweening overweigh overweight overwhelm overwhelmed overwhelming overwind overwinter overwire overwise over with overwithhold overword overwore overwork overworn overwrite overwrought overzealous Oveta Ovett ovi- ovicide Ovid oviduct Oviedo oviferous oviform Ovimbundu ovine ovipara oviparous oviposit oviposition ovipositor ovisac OV language ovo- ovoid ovolactarian ovo-lacto-vegetarian ovolo ovonic ovonics ovotestis ovovitellin ovoviviparous Ovshinsky effect ovular ovulate ovulation ovulation method ovule ovum ow Owatonna owe owelty Owen Owen gun Owenism Owens Owens, Jesse Owensboro Owen Sound Owen Stanley Owen Stanley Range ower Owerri OWI owie owing owl owl's claws owl's clover owl butterfly owlet owlet moth owlet nightjar owlish owl monkey own own brand owner owner-occupied owner-occupier owner-operator ownership ownership flat own goal own medicine own person, be one's own up Owosso owse owt ox ox- Ox. oxa- oxacillin oxalate oxalic oxalic acid oxalis oxaloacetic acid oxalosuccinic acid oxazepam oxazine oxblood oxbow oxbow chest oxbow front oxbow lake Oxbridge oxcart oxen Oxenstierna oxeye ox-eyed oxeye daisy ox-eye herring OXFAM oxford Oxford Oxford accent Oxford and Cambridge Universities Oxford bags Oxford blue Oxford comma Oxford corners Oxford English Oxford frame Oxford gray Oxford Group Oxford movement Oxford Movement Oxford rule Oxfordshire Oxford shoe Oxford theory oxheart oxhide oxidane oxidant oxidant smog oxidase oxidate oxidation oxidation potential oxidation-reduction oxidation state oxidative oxidative phosphorylation oxidative stress oxide oxidimetry oxidize oxidizer oxidizing agent oxidoreductase oxime oximeter oximetry oxisol oxlip Oxnard Oxo oxo- oxo acid Oxon Oxon. Oxon Hill Oxonian oxonium compound oxo process oxpecker oxtail oxter oxtongue ox-tongue partisan Oxus oxy- oxyacetylene oxyacetylene torch oxyacid oxyaldehyde oxybenzene oxybenzone oxycalcium oxycalcium light oxycellulose oxycephaly oxychloride oxycodone oxycodone hydrochloride OxyContin oxygen oxygen acid oxygenase oxygenate oxygenation oxygenator oxygen bar oxygen cycle oxygen debt oxygen effect oxygenize oxygen lance oxygen mask oxygen tent oxygen weed oxyhaemoglobin oxyhemoglobin oxyhydrogen oxymetazoline oxymoron oxymorphone oxyneurine oxyntic oxyphilic oxysalt oxysulfide oxysulphide oxytetracycline oxytocia oxytocic oxytocin oxytone oxyuriasis oy Oyama Oyashio Current oyelet oyer oyer and terminer oyez oy gevalt Oyo oyster Oyster Bay oyster bed oyster cap oystercatcher oyster crab oyster cracker oystered oyster farm oysterfish oyster fork oystering oysterman oyster mushroom oyster pink oyster plant oystershell scale oysters Rockefeller oyster white oysterwoman oy vey oz Oz oz. oz. ap. oz. av. oz. t. Özal Ozalid Ozark Ozark Mountains Ozarks Ozawa Ozenfant Ozero Baykal ozo- ozocerite ozon- ozonation ozone ozone-friendly ozone hole ozone layer ozone sickness ozonic ether ozonide ozoniferous ozonize ozonizer ozono- ozonolysis ozonosphere ozonous ozostomia ozs ozs. ozzie Ozzie oˈcclusive oˈstensibly