1889. Pall Mall Gazette, Sept. 21, p. 3, col. 1 (In a London Gambling Hell). The flats who play faro (Cross-heading). 2. (American thieves’).—An honest man. 3. (American). A lover’s dismissal; a jilting. Adj. (colloquial and literary).—Downright; plain; straightforward; as in that’s flat? a flat lie, “flat burglary,” etc. 1598. Shakspeare, 1 King Henry IV., Act I., Sc. 3. Wor.: You start away, And lend no ear to my purposes. Those prisoners you shall keep. Hot.: Nay, I will; that’s flat. 1835–40. Haliburton, The Clockmaker, p. 6, preface (ed. 1862). 1848. Lowell, Fable for Critics, p. 19. (A fetch, I must say, most transparent and flat). [There are other usages, more or less colloquial: e.g., Insipid; tame; dull: as in Macaulay’s “flat as champagne in decanters.” On the Stock Exchange. flat = without interest: Stock is borrowed flat when no interest is allowed by the lender as security for the due return of the scrip.] Verb (American). To jilt. Cf., subs., sense 3. For synonyms, see Mitten. 1871. De Vere, Americanisms, p. 602. To flat, in the West, means to jilt, and is probably derived from another slang phrase, ‘to feel flat,’ denoting the depression which is apt to follow such a disappointment. To feel flat, verb. phr. (American).—1. To be low-spirited; out of sorts; off colour (q.v.). 1838. J. C. Neal, Charcoal Sketches. Not to hurt a gentleman’s feelings and to make him feel flat afore the country. 2. (American).—To fail; to give way. Also used substantively. Flat as a flounder (or Pancake), phr. (colloquial).—Very flat indeed. Also flat as be blowed. 1882. Punch, vol. LXXXII., p. 177, col. 1. To brush up a flat. See Brusher. To pick up a flat, verb. phr. (prostitutes’). To find a client. Fr., lever or faire un miché (miche = bread, from michon = money. Compare Breadwinner: under Monosyllable (q.v.)). 1869. Greenwood, Seven Curses of London. On the chance that she will, in the course of the evening, pick up a flat. To have (or do) a bit of flat, verb. phr. (venery).—To indulge in sexual intercourse. For synonyms, see Greens and Ride. Flat-back, subs. (common).—A bed-bug. For synonyms, see Norfolk Howard. Flat-broke, adj. (colloquial).—Utterly ruined; dead-broke (q.v.). Flat-catcher, subs. (common).—An impostor. 1823. Moncrieff, Tom and Jerry, i., 6. Cope (speaking of a horse). Well, Master Gull’em, do you think we shall get the flat-catcher off to-day? 1841. Blackwood’s Mag., l., 202. Buttoners are those accomplices of thimble-riggers ... whose duty it is to act as flat-catchers or decoys, by personating flats. 1856. Mayhew, Great World of London, p. 46. And flat-catchers, or ‘ring-droppers,’ who cheat by pretending to find valuables in the street. 1864. London Review, June 18, p. 643. ‘The Bobby’ or chinked-back horse, is another favourite flat-catcher.