[ flat ]
See synonyms for: flatflatsflatterflatly on Thesaurus.com

adjective,flat·ter, flat·test.
  1. horizontally level:a flat roof.

  2. level, even, or without unevenness of surface, as land or tabletops.

  1. having a surface that is without marked projections or depressions: a broad, flat face.

  2. lying horizontally and at full length, as a person; prostrate: He was flat on the canvas after the knockdown.

  3. lying wholly on or against something: The banner was flat against the wall.

  4. thrown down, laid low, or level with the ground, as fallen trees or buildings.

  5. having a generally level shape or appearance; not deep or thick: a flat plate.

  6. (of the heel of a shoe) low and broad.

  7. spread out, as an unrolled map or the open hand.

  8. deflated; collapsed: a flat tire.

  9. absolute, downright, or positive; without qualification: a flat denial.

  10. without modification or variation: a flat rate.

  11. Informal. lacking money; broke.

  12. without vitality or animation; lifeless; dull: flat writing.

  13. having lost its flavor, sharpness, or life, as wine or food; stale.

  14. (of a beverage) having lost its effervescence.

  15. without flavor; not spiced: flat cooking.

  16. prosaic, banal, or insipid: a flat style.

  17. pointless, as a remark or joke.

  18. commercially inactive: a flat day in the stock market.

  19. (of a painting) not having the illusion of volume or depth.

  20. (of a photograph or painting) lacking contrast or gradations of tone or color.

  21. (of paint) without gloss; not shiny; mat.

  22. not clear, sharp, or ringing, as sound or a voice.

  23. lacking resonance and variation in pitch; monotonous: a flat delivery of the speech.

  24. Music.

    • (of a tone) lowered a half step in pitch: B flat.

    • below an intended pitch, as a note; too low (opposed to sharp).

  25. Grammar. derived without change in form, as English to brush from the noun brush and adverbs that do not add -ly to the adjective form as fast, cheap, and slow.

  26. Phonetics. lenis; voiced.

  27. Nautical. (of a sail)

    • cut with little or no fullness.

    • trimmed as nearly fore-and-aft as possible, for sailing to windward.

  28. flat a, the a-sound (a) of glad, bat, or act.

  1. something flat.

  2. a shoe, especially a woman's shoe, with a flat heel or no heel.

  1. a flat surface, side, or part of anything: He struck me with the flat of his hand.

  2. flat or level ground; a flat area: salt flats.

  3. a marsh, shoal, or shallow.

  4. Music.

    • (in musical notation) the character ♭, which when attached to a note or to a staff degree lowers its significance one chromatic half step.

    • a tone one chromatic half step below another: The flat of B is B flat.

    • (on keyboard instruments, with reference to any given note) the key next below or to the left.

  5. Theater. a piece of scenery consisting of a wooden frame, usually rectangular, covered with lightweight board or fabric.

  6. a broad, thin book, chiefly for children: a juvenile flat.

  7. Informal. a deflated automobile tire.

  8. (in postal use) a large flat package, as in a manila envelope, for mailing.

  9. Architecture. a flat roof or deck.

  10. Nautical.

    • Also called platform . a partial deck between two full decks.

    • a low, flat barge or lighter.

  11. Shipbuilding.

    • a broad, flat piece of iron or steel for overlapping and joining two plates at their edges.

    • a straight timber in a frame or other assembly of generally curved timbers.

  12. an iron or steel bar of rectangular cross section.

  13. Textiles. one of a series of laths covered with card clothing, used in conjunction with the cylinder in carding.

  14. Photography. one or more negatives or positives in position to be reproduced.

  15. Printing. a device for holding a negative or positive flat for reproduction by photoengraving.

  16. Horticulture. a shallow, lidless box or tray used for rooting seeds and cuttings and for growing young plants.

  17. a similar box used for shipping and selling fruits and vegetables.

  18. Football. the area of the field immediately inside of or outside of an offensive end, close behind or at the line of scrimmage.

  19. flats, Informal. flat races between horses.: Compare flat race.

verb (used with object),flat·ted, flat·ting.
  1. to make flat.

  2. Music. to lower (a pitch), especially one half step.

verb (used without object),flat·ted, flat·ting.
  1. to become flat.

  1. in a flat position; horizontally; levelly.

  2. in a flat manner; positively; absolutely.

  1. completely; utterly: flat broke.

  2. exactly; precisely: She ran around the track in two minutes flat.

  3. Music. below the true pitch: to sing flat.

  4. Finance. without interest.

Verb Phrases
  1. flat in, Nautical. to pull the clew of (a fore-and-aft sail) as nearly amidships as possible.: Also flatten in.

Idioms about flat

  1. fall flat, to fail to produce the desired effect; fail completely: His attempts at humor fell flat.

  2. flat aft, Nautical. trimmed so that fore-and-aft sails present as flat a surface as possible, as in sailing close to the wind.

  1. flat on one's back. back1 (def. 48).

  2. flat out, Informal.

    • without hesitation; directly or openly: He told us flat out he'd been a double agent.

    • at full speed or with maximum effort.

Origin of flat

First recorded in 1275–1325; Middle English, from Old Norse flatr; akin to Old English flet “the ground, a floor of a house,” Greek platýs “wide, broad”; see also flat2; plate

synonym study For flat

1. See level.

Other words for flat

Opposites for flat

Other words from flat

  • flatly, adverb
  • flatness, noun
  • un·flat·ted, adjective

Words Nearby flat

Other definitions for flat (2 of 2)

[ flat ]

nounChiefly British.
  1. an apartment or suite of rooms on one floor forming a residence.

Origin of flat

First recorded in 1795–1805; variant of obsolete flet, from Old English; see origin at flat1

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use flat in a sentence

British Dictionary definitions for flat (1 of 2)


/ (flæt) /

adjectiveflatter or flattest
  1. horizontal; level: flat ground; a flat roof

  2. even or smooth, without projections or depressions: a flat surface

  1. lying stretched out at full length; prostrate: he lay flat on the ground

  2. having little depth or thickness; shallow: a flat dish

  3. (postpositive often foll by against) having a surface or side in complete contact with another surface: flat against the wall

  4. spread out, unrolled, or levelled

  5. (of a tyre) deflated, either partially or completely

  6. (of shoes) having an unraised or only slightly raised heel

  7. mainly British

    • (of races, racetracks, or racecourses) not having obstacles to be jumped

    • of, relating to, or connected with flat racing as opposed to steeplechasing and hurdling: flat jockeys earn more

  8. without qualification; total: a flat denial

  9. without possibility of change; fixed: a flat rate

  10. (prenominal or immediately postpositive) neither more nor less; exact: he did the journey in thirty minutes flat; a flat thirty minutes

  11. unexciting or lacking point or interest: a flat joke

  12. without variation or resonance; monotonous: a flat voice

  13. (of food) stale or tasteless

  14. (of beer, sparkling wines, etc) having lost effervescence, as by exposure to air

  15. (of trade, business, a market, etc) commercially inactive; sluggish

  16. (of a battery) fully discharged; dead

  17. (of a print, photograph, or painting) lacking contrast or shading between tones

  18. (of paint) without gloss or lustre; matt

  19. (of a painting) lacking perspective

  20. (of lighting) diffuse

  21. music

    • (immediately postpositive) denoting a note of a given letter name (or the sound it represents) that has been lowered in pitch by one chromatic semitone: B flat

    • (of an instrument, voice, etc) out of tune by being too low in pitch: Compare sharp (def. 12)

  22. phonetics another word for lenis

  23. flat a phonetics the vowel sound of a as in the usual US or S Brit pronunciation of hand, cat, usually represented by the symbol (æ)

  1. in or into a prostrate, level, or flat state or position: he held his hand out flat

  2. completely or utterly; absolutely: he went flat against the rules

  1. exactly; precisely: in three minutes flat

  2. music

    • lower than a standard pitch

    • too low in pitch: she sings flat Compare sharp (def. 18)

  3. fall flat to fail to achieve a desired effect, etc

  4. flat out informal

    • with the maximum speed or effort

    • totally exhausted

  1. a flat object, surface, or part

  2. (often plural) a low-lying tract of land, esp a marsh or swamp

  1. (often plural) a mud bank exposed at low tide

  2. music

    • an accidental that lowers the pitch of the following note by one chromatic semitone: Usual symbol:

    • a note affected by this accidental: Compare sharp (def. 19)

  3. theatre a rectangular wooden frame covered with painted canvas, etc, used to form part of a stage setting

  4. a punctured car tyre

  5. the flat mainly British ((often cap.))

    • flat racing, esp as opposed to steeplechasing and hurdling

    • the season of flat racing

  6. nautical a flatboat or lighter

  7. US and Canadian a shallow box or container, used for holding plants, growing seedlings, etc

verbflats, flatting or flatted
  1. to make or become flat

  2. music the usual US word for flatten (def. 3)

Origin of flat

C14: from Old Norse flatr; related to Old High German flaz flat, Greek platus flat, broad

Derived forms of flat

  • flatly, adverb
  • flatness, noun

British Dictionary definitions for flat (2 of 2)


/ (flæt) /

  1. a set of rooms comprising a residence entirely on one floor of a building: Usual US and Canadian name: apartment

  2. British and NZ a portion of a house used as separate living quarters

  1. NZ a house shared with people who are not members of one's own family

verbflats, flatting or flatted (intr)
  1. Australian and NZ to live in a flat (with someone)

Origin of flat

Old English flett floor, hall, house; related to flat 1

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

Other Idioms and Phrases with flat


In addition to the idioms beginning with flat

  • flat as a pancake
  • flat broke
  • flat on one's back
  • flat out

also see:

  • caught flat-footed
  • fall flat
  • in no time (nothing flat)
  • leave flat

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.