fly blind,
    1. to operate an airplane, especially during conditions of poor visibility, relying solely on instruments for guidance.
    2. to proceed with a complex task in the absence of directions by using one's own ability to determine what procedures to follow.
    fly in the face of, to act in defiance of (authority, custom, etc.).Also fly in the teeth of.
    fly off the handle. handle(def 16).
    go fly a kite, Slang.
    1. to put up with or get used to matters as they stand.
    2. to confine oneself to one's own affairs.
    3. to cease being a nuisance: If she gets mad enough she'll tell me to go fly a kite.
    let fly,
    1. to hurl or propel (a weapon, missile, etc.).
    2. to give free rein to an emotion: She let fly with a barrage of angry words.
    on the fly,
    1. during flight; before falling to the ground: to catch a baseball on the fly.
    2. hurriedly; without pausing: We had dinner on the fly.

Origin of fly

before 900; Middle English flīen, Old English flēogan; cognate with Old High German fliogan, German fliegen, Old Norse fljuga
Related formsfly·a·ble, adjectivefly·a·bil·i·ty, nounnon·fly·a·ble, adjectivere·fly·a·ble, adjectiveun·fly·a·ble, adjective

Synonyms for fly

1. Fly, flit, flutter, hover, soar refer to moving through the air as on wings. Fly is the general term: Birds fly. Airplanes fly. To flit is to make short rapid flights from place to place: A bird flits from tree to tree. To flutter is to agitate the wings tremulously, either without flying or in flying only short distances: A young bird flutters out of a nest and in again. To hover is to linger in the air, or to move over or about something within a narrow area or space: hovering clouds; a hummingbird hovering over a blossom. To soar is to (start to) fly upward to a great height usually with little advance in any other direction, or else to (continue to) fly at a lofty height without visible movement of the wings: Above our heads an eagle was soaring.



noun, plural flies.

Also called true fly. any of numerous two-winged insects of the order Diptera, especially of the family Muscidae, as the common housefly.
any of various winged insects, as the mayfly or firefly.
Angling. a fishhook dressed with hair, feathers, silk, tinsel, etc., so as to resemble an insect or small fish, for use as a lure or bait.
(initial capital letter) Astronomy. the constellation Musca.

Origin of fly

before 950; Middle English flīe, Old English flēoge, flȳge; cognate with Middle Dutch vliege (Dutch vlieg), Old High German flioga (German Fliege); akin to fly1
Related formsfly·less, adjective



adjective British Informal.

clever; keen; ingenious.
agile; nimble.

Origin of fly

First recorded in 1805–15; perhaps special use of fly1 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for fly

Contemporary Examples of fly

Historical Examples of fly

  • It was in one of his fits of rage and remorse that Charley had asked Cherrie to fly with him.

    A Changed Heart

    May Agnes Fleming

  • He will fly back southeast along the lakeshore to the meeting place.

  • Sam was already on the run, and, coming to the turn in the road, he let fly several snowballs.

    The Rover Boys on a Tour

    Arthur M. Winfield

  • They were to fly the American flag; that, too, should mean a subsidy.

    The President

    Alfred Henry Lewis

  • In captivity, having no web, it actually flees before its prey, and has not the resolution to confront a fly.

    The Insect

    Jules Michelet

British Dictionary definitions for fly



verb flies, flying, flew or flown

(intr) (of birds, aircraft, etc) to move through the air in a controlled manner using aerodynamic forces
to travel over (an area of land or sea) in an aircraft
to operate (an aircraft or spacecraft)
to float, flutter, or be displayed in the air or cause to float, etc, in this wayto fly a kite; they flew the flag
to transport or be transported by or through the air by aircraft, wind, etc
(intr) to move or be moved very quickly, forcibly, or suddenlyshe came flying towards me; the door flew open
(intr) to pass swiftlytime flies
to escape from (an enemy, place, etc); fleehe flew the country
(intr; may be foll by at or upon) to attack a person
(intr) to have a sudden outbursthe flew into a rage again
(intr) (of money, etc) to vanish rapidly
(tr) falconry (of hawks) to fly at (quarry) in attackperegrines fly rooks
(tr) theatre to suspend (scenery) above the stage so that it may be lowered into view
fly a kite
  1. to procure money by an accommodation bill
  2. to release information or take a step in order to test public opinion
fly high informal
  1. to have a high aim
  2. to prosper or flourish
fly in the face of See face (def. 19)
fly off the handle informal to lose one's temper
fly the coop US and Canadian informal to leave suddenly
go fly a kite US and Canadian informal go away
let fly informal
  1. to lose one's temper (with a person)she really let fly at him
  2. to shoot or throw (an object)

noun plural flies

Also called: fly front (often plural) a closure that conceals a zip, buttons, or other fastening, by having one side overlapping, as on trousers
Also called: fly sheet
  1. a flap forming the entrance to a tent
  2. a piece of canvas drawn over the ridgepole of a tent to form an outer roof
a small air brake used to control the chiming of large clocks
the horizontal weighted arm of a fly press
  1. the outer edge of a flag
  2. the distance from the outer edge of a flag to the staffCompare hoist (def. 9)
British a light one-horse covered carriage formerly let out on hire
Australian and NZ an attemptI'll give it a fly
  1. a device for transferring printed sheets from the press to a flat pile
  2. Also called: flyhanda person who collects and stacks printed matter from a printing press
  3. a piece of paper folded once to make four pages, with printing only on the first page
(plural) theatre the space above the stage out of view of the audience, used for storing scenery, etc
rare the act of flying
Derived Formsflyable, adjective

Word Origin for fly

Old English flēogan; related to Old Frisian fliāga, Old High German fliogan, Old Norse fljūga



noun plural flies

any dipterous insect, esp the housefly, characterized by active flightSee also horsefly, blowfly, tsetse fly, crane fly
any of various similar but unrelated insects, such as the caddis fly, firefly, dragonfly, and chalcid fly
angling a lure made from a fish-hook dressed with feathers, tinsel, etc, to resemble any of various flies or nymphs: used in fly-fishingSee also dry fly, wet fly
(in southern Africa) an area that is infested with the tsetse fly
drink with the flies Australian slang to drink alone
fly in amber See amber (def. 2)
fly in the ointment informal a slight flaw that detracts from value, completeness, or enjoyment
fly on the wall a person who watches others, while not being noticed himself or herself
there are no flies on him informal he is no fool
Derived Formsflyless, adjective

Word Origin for fly

Old English flēoge; related to Old Norse fluga Old High German flioga; see fly 1



adjective flyer or flyest slang

mainly British knowing and sharp; smart
mainly Scot furtive or sneaky


on the fly mainly Scot in secret; sneakily

Word Origin for fly

C19: of uncertain origin
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for fly

Old English fleoge "fly, winged insect," from Proto-Germanic *fleugjon (cf. Old Saxon fleiga, Old Norse fluga, Middle Dutch vlieghe, Dutch vlieg, Old High German flioga, German Fliege "fly); literally "the flying (insect)" (cf. Old English fleogende "flying"), from same source as fly (v.1).

Originally any winged insect (hence butterfly, etc.); long used by farmers and gardeners for any insect parasite. The Old English plural in -n (cf. oxen) gradually normalized 13c.-15c. to -s. Fly on the wall "unseen observer" first recorded 1881. An Old English word for "curtain" was fleonet "fly-net." Fly-swatter first attested 1917. Fly-fishing is from 1650s.


"to soar through air," Old English fleogan "to fly" (class II strong verb; past tense fleag, past participle flogen), from West Germanic *fleuganan (cf. Old Saxon and Old High German fliogan, Old Norse flügja, Old Frisian fliaga, Middle Dutch vlieghen, Dutch vliegen, German fliegen), from PIE *pleu- "flowing, floating" (see pluvial).

Notion of "flapping as a wing does" led to noun sense of "tent flap" (1810), which yielded (1844) "covering for buttons that close up a garment." The noun sense of "a flight, flying" is from mid-15c. Baseball fly ball attested by 1866. Slang phrase fly off the handle "lose one's cool" dates from 1825. To do something on the fly is 1856, apparently from baseball.


"run away," Old English fleon (see flee). Fleogan and fleon were often confused in Old English, too. Modern English distinguishes in preterite: flew/fled.


slang, "clever, alert, wide awake," late 18c., perhaps from fly (n.) on the notion of the insect being hard to catch. Other theories, however, trace it to fledge or flash. Slang use in 1990s might be a revival or a reinvention.

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for fly




Any of numerous two-winged insects of the order Diptera.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for fly



Any of numerous insects of the order Diptera, having one pair of wings and large compound eyes. Flies include the houseflies, horseflies, and mosquitoes. See more at dipteran.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.