flat

¹ American  

[flat] / flæt /

adjective

flatter, flattest

1. horizontally level.

   a flat roof.

   Synonyms:

   plane

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

3. having a surface that is without marked projections or depressions.

   a broad, flat face.

4. lying horizontally and at full length, as a person; prostrate.

   He was flat on the canvas after the knockdown.

   Synonyms:

   prone, low

   Antonyms:

   vertical, upright

5. lying wholly on or against something.

   The banner was flat against the wall.

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

7. having a generally level shape or appearance; not deep or thick.

   a flat plate.

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

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

10. deflated; collapsed.

    a flat tire.

11. absolute, downright, or positive; without qualification.

    a flat denial.

    Synonyms:

    categorical, peremptory, outright

12. without modification or variation.

    a flat rate.

13. Informal. lacking money; broke.

14. without vitality or animation; lifeless; dull.

    flat writing.

    Synonyms:

    prosaic, spiritless, boring

    Antonyms:

    spirited

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

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

17. without flavor; not spiced.

    flat cooking.

    Synonyms:

    unsavory, vapid

    Antonyms:

    savory, flavorful

18. prosaic, banal, or insipid.

    a flat style.

19. pointless, as a remark or joke.

20. commercially inactive.

    a flat day in the stock market.

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

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

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

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

25. lacking resonance and variation in pitch; monotonous.

    a flat delivery of the speech.

26. Music.

    1. (of a tone) lowered a half step in pitch.

       B flat.

    2. below an intended pitch, as a note; too low (sharp ).

27. 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.

28. Phonetics. lenis; voiced.

29. Nautical. (of a sail)

    1. cut with little or no fullness.

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

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

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noun

1. something flat.

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

3. a flat surface, side, or part of anything.

   He struck me with the flat of his hand.

4. flat or level ground; a flat area.

   salt flats.

5. a marsh, shoal, or shallow.

6. Music.

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

   2. a tone one chromatic half step below another.

      The flat of B is B flat.

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

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

8. a broad, thin book, chiefly for children.

   a juvenile flat.

9. Informal. a deflated automobile tire.

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

11. Architecture. a flat roof or deck.

12. Nautical.

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

    2. a low, flat barge or lighter.

13. Shipbuilding.

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

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

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

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

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

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

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

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

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

21. Informal. flats, flat races between horses.

verb (used with object)

flatted, flatting

1. to make flat.

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

verb (used without object)

flatted, flatting

1. to become flat.

adverb

1. in a flat position; horizontally; levelly.

2. in a flat manner; positively; absolutely.

3. completely; utterly.

   flat broke.

4. exactly; precisely.

   She ran around the track in two minutes flat.

5. Music. below the true pitch.

   to sing flat.

6. Finance. without interest.

verb phrase

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

idioms

1. fall flat, to fail to produce the desired effect; fail completely.

   His attempts at humor fell flat.

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

3. flat out,

   1. without hesitation; directly or openly.

      He told us flat out he'd been a double agent.

   2. at full speed or with maximum effort.

4. flat on one's back. back.

flat ² American  

[flat] / flæt /

noun

Chiefly British.

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

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flat ¹ British  

/ flæt /

adjective

1. horizontal; level

   flat ground

   a flat roof

2. even or smooth, without projections or depressions

   a flat surface

3. lying stretched out at full length; prostrate

   he lay flat on the ground

4. having little depth or thickness; shallow

   a flat dish

5. having a surface or side in complete contact with another surface

   flat against the wall

6. spread out, unrolled, or levelled

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

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

9. 1. (of races, racetracks, or racecourses) not having obstacles to be jumped

   2. of, relating to, or connected with flat racing as opposed to steeplechasing and hurdling

      flat jockeys earn more

10. without qualification; total

    a flat denial

11. without possibility of change; fixed

    a flat rate

12. (prenominal or immediately postpositive) neither more nor less; exact

    he did the journey in thirty minutes flat

    a flat thirty minutes

13. unexciting or lacking point or interest

    a flat joke

14. without variation or resonance; monotonous

    a flat voice

15. (of food) stale or tasteless

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

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

18. (of a battery) fully discharged; dead

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

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

21. (of a painting) lacking perspective

22. (of lighting) diffuse

23. music

    1. (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

    2. (of an instrument, voice, etc) out of tune by being too low in pitch Compare sharp

24. phonetics another word for lenis

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

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adverb

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

3. exactly; precisely

   in three minutes flat

4. music

   1. lower than a standard pitch

   2. too low in pitch Compare sharp

      she sings flat

5. to fail to achieve a desired effect, etc

6. informal

   1. with the maximum speed or effort

   2. totally exhausted

noun

1. a flat object, surface, or part

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

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

4. music

   1. an accidental that lowers the pitch of the following note by one chromatic semitone

   2. a note affected by this accidental Compare sharp

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

6. a punctured car tyre

7. ((often cap.))

   1. flat racing, esp as opposed to steeplechasing and hurdling

   2. the season of flat racing

8. nautical a flatboat or lighter

9. a shallow box or container, used for holding plants, growing seedlings, etc

verb

1. to make or become flat

2. music the usual US word for flatten

flat ² British  

/ flæt /

noun

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

2. a portion of a house used as separate living quarters

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

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verb

1. to live in a flat (with someone)

flat More Idioms  

More idioms and phrases containing flat

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

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Related Words

See level.

Other Word Forms

• flatly adverb
• flatness noun
• unflatted adjective

Etymology

Origin of flat¹

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”; flat ²; plate

Origin of flat²

First recorded in 1795–1805; variant of obsolete flet, from Old English; flat ¹

Explanation

A flat is an apartment. It's called a flat because all the rooms in it are usually on the same floor. The word flat is much more common in British than American English. Geometrically, something flat is an even, level plane, like Kansas relative to the Rocky Mountains, or the cargo area of a flatbed truck. As an adjective, flat means "less than lively." A flat soda has no bubbles. If your speech falls flat, no one was excited. If you get mugged you might choose to lie flat on the ground. A flat note is just below the right pitch. And if your cooking is flat, it's boring.

Example Sentences

But remember, Wall Street analysts are expecting the S&P 500 to deliver profit growth of more than 17% this year—not flat to slightly up.

From Barron's • Apr. 15, 2026

The dollar was flat while sovereign bond yields edged lower in the U.S. and Europe in response.

From The Wall Street Journal • Apr. 15, 2026

The Buckeye State has been pulling its income-tax rates lower and switched to a flat 2.75% rate this year.

From MarketWatch • Apr. 15, 2026

In a subsequent statement in Parliament, Defence Minister Luke Pollard insisted the government was "not waiting" on the investment plan to announce further defence projects, but was "working flat out to" get the document published.

From BBC • Apr. 15, 2026

We were unable to move to the professor’s flat, and we stayed in our home until we were turned out and landed in Kazimierz.

From "Not Nothing" by Gayle Forman

Related Words

• bland
• dead
• lifeless
• stale
• weak