Green’s Dictionary of Slang

1. (also flaps) a promiscuous woman; a prostitute.

1631		J. Mabbe (trans.) Celestina IX 110: Fall to your flap, my Masters, kisse and clip. [Ibid.] 112: Come hither, you foule flappes.
1657		T. Jordan Walks of Islington and Hogsdon IV i: A Babylonish Garment, or in good sooth and verily a wicked and superstitious remnant of that foul flaps the whore of Babylon.
1671		‘The Kind Husband’ in Ebsworth Westminster Drolleries (1875) 46: Nay, I’ll make you wait, you Flaps.
1914		Jackson & Hellyer Vocab. Criminal Sl. 34: flap [...] Current amongst pimps and criminals who are contemptous of female values. An opprobrious epithet for loose women.
1950		Goldin et al. DAUL 71/1: Flap. A loose woman.

2. any garment that has a pendant flap or flaps.

1984

Partridge DSUE (8th edn) 400/2: ca. 1790–1920.

3. (UK Und.) strips of lead used on roofs.

1873		Sl. Dict.
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1890–1904		Farmer & Henley Sl. and Its Analogues.

4. the vagina.

1890–1904		Farmer & Henley Sl. and Its Analogues.
1914		Jackson & Hellyer Vocab. Criminal Sl. 34: flap [...] the female sex organ.

5. (also hearing flap, side-flap) an ear, usu. large.

1885		Bulletin (Sydney) 15 Aug. 17/2: It’s too thin, Ballington – far too thin. Throw your ‘side-flaps’ well back, and listen. We would speak with you.
1910		Truth (Brisbane) 4 Dec. 11/3: ‘N’ p’raps when y’r cock y’r listener flaps frum under th’ nap, its a moral th’ prattlin’ ’alf is chantin verse mewsic in ‘er dreams.
1934		B. Traven Death Ship 333: At the first dim crackling my hearing flap catches, I shall be up and out.
1944		D. Burley N.Y. Amsterdam News 16 Sept. 12A: I wanna spiel about the way I feel into one of them fine flaps o’ yourn.
1944		J. Cary Horse’s Mouth (1948) 16: When I was a kid, and I got earache, I used to say, go on, ache; go on, you bloody flap Give me hell.
1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 175: ‘Flaps’ or ‘lugs’ for ears.
1977		D. Powis Signs of Crime 183: Flaps [...] Often a nickname for a man with large ears.

6. in pl., the labia majora.

1888–94		‘Walter’ My Secret Life (1966) VI 1149: Men, she was sure, didn’t like those flaps.
1989		Viz June/July 25: Just open your flaps a little so as I can pop it in!!
1998		I. Welsh Filth 219: Women are like tetrapaks: it isnae what’s inside that’s important, the crucial thing is tae git those flaps open.
2001		I. Welsh Glue 41: Ah’m pullin her wee flaps apart and giein it big postage stamp licks.
2007		R. Milward Apples (2023) 197: [I]t was her getting her flaps out out all the time.
2012		(con. 1980s) I. Welsh Skagboys 26: He sports these huge jowls that look like vagina flaps.
2017		Women’s March Poster 21 Jan. Sick of Chaps / Policing Our Flaps.

7. (US black) a door.

1948

D. Burley N.Y. Amsterdam News 10 Jan. 17: ‘Flap’ is the door.

8. (US) the mouth.

1954		J.E. Macdonnell Jim Brady 196: Get it orf yer chest or else button yer bloody flap.
1966		M. Rumaker Exit 3 and Other Stories 70: Shut your flap, Ruby.
1974		(con. 1940s) E. Thompson Tattoo (1977) 124: Somebody’s going to slap a button on that flap.

9. (Aus.) a cheque.

1951		E. Hill Territory 444: False flaps: Bad cheques.
1983		R. Aven-Bray Ridgey-Didge Oz Jack Lang 28: Flaps Cheques.