flatness Definition

flat¹
adj flatter, flattest

1. Level; horizontal; even.

Thesaurus: level, even, smooth, spread out, extended, horizontal.
2. Without hollows or prominences.
3. Lacking the usual prominence.

Example: a flat nose
4. Not bent or crumpled.
5. Said of feet: having little or no arch to the instep of the foot, so that the sole lies flat against the ground.
6. Said of shoes: not having a raised heel.
7. Bored; depressed.
8. Dull; not lively.
9. Toneless and expressionless.
10. colloq
Definite; downright; emphatic.
Example: a flat refusal
11a. music.
Said of an instrument, voice, etc: lower than the correct pitch;
11b. music.
That lowers the specified note by a semitone. Compare sharp adj 13.
Example: C flat
Example: C ♭
12. Said of a tyre: having too little air in it.

Example: The tyre went flat
13. Said of a drink: having lost its fizziness.
14. Said of a battery: having little or no electrical charge remaining.
15. Said of a price, rate, economic indicator, etc: fixed; unvarying.
16. Said of a business, company, etc: commercially inactive.
17. Said of paint: matt, not glossy.

adverb

1. Stretched out rather than curled up, crumpled, etc.
2. Into a flat compact shape.

Example: folds flat for storage
3. Exactly.

Example: in two minutes flat
4. Bluntly and emphatically.

Example: I can tell you flat
5. music.
At lower than the correct pitch.
Example: He sang flat

noun

1. Something flat; a flat surface or part.
2a. An area of flat land;

Thesaurus: marsh, swamp, lowland, morass, moss, plain.
Form: flats
2b. A mud bank exposed at low tide.

Thesaurus: mud flat, shoal, shallow, strand.
Form: flats
3. colloq
A punctured tyre on a vehicle.
Example: Oh no! We've got another flat
4a. music.
A sign (♭) that lowers a note by a semitone from the note that it refers to;
4b. music.
A note lowered in this way.
5. A flat upright section of stage scenery slid or lowered onto the stage.
6a. horse-racing.
flat racing;
Form: the flat
6b. horse-racing.
The season of flat racing, from March to November.
Form: the flat

Derivative: flatly
adverb

Emphatically.
Example: she flatly refused to go

Derivative: flatness
noun

Derivative: flattish
adj

Idiom: fall flat

colloq
To fail to achieve the hoped-for effect.
Example: The joke fell flat

Idiom: fall flat on one's face

colloq
To fail at something in a humiliating way.

Idiom: flat broke

colloq
Completely without money.

Idiom: flat out

colloq
With maximum speed and energy.
Example: They were all working flat out

Idiom: that's flat

colloq
That's certain or final.

Etymology: 14c: from Norse flatr flat.