flat¹ / flat/ • adj. (flat·ter, flat·test) 1. smooth and even; without marked lumps or indentations: a flat wall trim the surface of the cake to make it completely flat. ∎  (of land) without hills: thirty-five acres of flat countryside. ∎  (of an expanse of water) calm and without waves. ∎  not sloping: the flat roof of a garage. ∎  having a broad level surface but little height or depth; shallow: a flat rectangular box a flat cap. ∎  (of shoes) without heels or with very low heels. ∎  (of a woman) having small breasts.2. lacking interest or emotion; dull and lifeless: “I'm sorry,” he said, in a flat voice her drawings were flat and unimaginative. ∎  (of a person) without energy; dispirited: his sense of intoxication wore off until he felt flat and weary. ∎  (of a market, prices, etc.) showing little activity; sluggish: cash flow was flat at $214 million flat sales in the drinks industry. ∎  (of a sparkling drink) having lost its effervescence: flat champagne. ∎  (of something kept inflated, esp. a tire) having lost some or all of its air, typically because of a puncture: you've got a flat tire. ∎  (of a color) uniform: the dress was a deadly, flat shade of gray. ∎  (of a photographic print or negative) lacking contrast.3. (of a fee, wage, or price) the same in all cases, not varying with changed conditions or in particular cases: a $30 flat fare. See also flat rate. ∎  (of a denial, contradiction, or refusal) completely definite and firm; absolute: his statement was a flat denial that he had misbehaved.4. (of musical sound) below true or normal pitch. ∎  [in comb.] (of a note) a semitone lower than a specified note: the double basses' opening low E-flat you never have to change key from B-flat major. ∎  (of a key) having a flat or flats in the signature.5. (Flat) of or relating to flat racing: the Flat season.• adv. 1. in or to a horizontal position: he was lying flat on his back she had been knocked flat by the blast. ∎  lying in close juxtaposition, esp. against another surface: his black curly hair was blown flat across his skull. ∎  so as to become smooth and even: I hammered the metal flat.2. inf. completely; absolutely: I'm turning you down flat | she was going to be flat broke in a couple of days. ∎  after a phrase expressing a period of time to emphasize how quickly something can be done or has been done: you can prepare a healthy meal in ten minutes flat.3. below the true or normal pitch of musical sound: it wasn't a question of singing flat, but of simply singing the wrong notes.• n. 1. [in sing.] the flat part of something: she placed the flat of her hand over her glass.2. a flat object, in particular: ∎  (often flats) an upright section of painted stage scenery mounted on a frame. ∎ inf. a flat tire. ∎  a shallow container in which seedlings are grown and sold. ∎  (often flats) a shoe with a very low heel or no heel. ∎  a railroad car with a flat floor and no sides or roof; a flatcar.3. (usu. flats) an area of low level ground, esp. near water: the Utah salt flats. See also mudflat.4. a musical note lowered a semitone below natural pitch. ∎  the sign (♭) indicating this. • v. (flat·ted, flat·ting) [tr.] 1. [usu. as adj.] (flatted) Mus. lower (a note) by a semitone: “blue” harmony emphasizing the flatted third and seventh.2. archaic make flat; flatten: flat the loaves down.PHRASES: fall flat fail completely to produce the intended or expected effect: his jokes fell flat.fall flat on one's face fall over forward. ∎ fig. fail in an embarrassingly obvious way: the president could fall flat on his face if the economy doesn't start improving soon. (as) flat as a pancakesee pancake.flat out1. as fast or as hard as possible: the whole team is working flat out to satisfy demand | [as adj.] (flat-out) the album lacks the flat-out urgency of its predecessor. 2. inf. without hesitation or reservation; unequivocally: in those early days I'd just flat out vote against foreign aid | [as adj.] (flat-out) flat-out perjury. 3. lying completely stretched out, esp. asleep or exhausted: she was lying flat out on her pink bath towel.that's flat inf. used to indicate that one has reached a decision and will not be persuaded to change one's mind: he won't go into a home and that's flat.DERIVATIVES: flat·ness n.flat·tish / ˈflatish/ adj.flat² • n. British term for apartment.DERIVATIVES: flat·let / -lət/ n.

flat That part of a staircase thrust plane trajectory which has a horizontal or subhorizontal orientation. Flats represent areas of décollement (see DÉCOLLEMENT PLANE) along weak, layer- or bedding-parallel planes. Although initially horizontal, flats may steepen during later compression.See RAMP; and THRUST.

flat
♭. (♭). The sign which, placed before a note, lowers its pitch by a semitone. In Britain, the verb ‘to flatten’ (past participle ‘flattened’) is in use; in USA, ‘to flat’ (‘flatted’).

2. ‘Flat’ singing or playing is that which departs from correct intonation on the downward side.

flat2 storey of a house; suite of rooms on one floor. XIX. alt. by assoc. with prec. of Sc. flet inner part of a house (OE. flet floor, dwelling :- Gmc. *flatjam, f. *flataz FLAT1).

flat (symbol b) In musical notation, an accidental sign placed before a note or immediately after the clef to indicate that the note it refers to should be sounded a semitone lower.