Green’s Dictionary of Slang

flap n.1

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

J. Mabbe (trans.) Celestina IX 110: Fall to your flap, my Masters, kisse and clip. [Ibid.] 112: Come hither, you foule flappes.
[UK]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.
[UK] ‘The Kind Husband’ in Ebsworth Westminster Drolleries (1875) 46: Nay, I’ll make you wait, you Flaps.
[US]Jackson & Hellyer Vocab. Criminal Sl. 34: flap [...] Current amongst pimps and criminals who are contemptous of female values. An opprobrious epithet for loose women.
[US]Goldin et al. DAUL 71/1: Flap. A loose woman.

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

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

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

[UK]Sl. Dict.
[UK]Barrère & Leland Dict. of Sl., Jargon and Cant.
[UK]Farmer & Henley Sl. and Its Analogues.

4. the vagina.

[UK]Farmer & Henley Sl. and Its Analogues.
[US]Jackson & Hellyer Vocab. Criminal Sl. 34: flap [...] the female sex organ.

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

[Aus]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.
[Aus]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.
[US]B. Traven Death Ship 333: At the first dim crackling my hearing flap catches, I shall be up and out.
[US]D. Burley Orig. Hbk of Harlem Jive 102: I wanna spiel about the way I feel into one of them fine flaps o’ yourn.
[UK]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.
[UK]I. & P. Opie Lore and Lang. of Schoolchildren (1977) 175: ‘Flaps’ or ‘lugs’ for ears.
[UK]D. Powis Signs of Crime 183: Flaps [...] Often a nickname for a man with large ears.

6. in pl., the labia majora.

[UK]‘Walter’ My Secret Life (1966) VI 1149: Men, she was sure, didn’t like those flaps.
[UK]Viz June/July 25: Just open your flaps a little so as I can pop it in!!
[UK]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.
[UK]I. Welsh Glue 41: Ah’m pullin her wee flaps apart and giein it big postage stamp licks.
[UK](con. 1980s) I. Welsh Skagboys 26: He sports these huge jowls that look like vagina flaps.
Women’s March Poster 21 Jan. Sick of Chaps / Policing Our Flaps.

7. (US) the mouth.

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

8. (Aus.) a cheque.

[UK]E. Hill Territory 444: False flaps: Bad cheques.
[Aus]R. Aven-Bray Ridgey-Didge Oz Jack Lang 28: Flaps Cheques.

In compounds

flap-cap (n.)

a whore.

[UK]N. Ward London Spy XV 368: You will never find one in their Custody above a Flap-Cap or a Cinder-Wench.
flap shot (n.) [SE shot, a picture]

in pornographic still or moving pictures, a close-up shot of the labia and open vagina.

[US]D. Smith Steely Blue 32: She has to get used to seeing...flap shots in the centerfolds [HDAS].
posting at www.bondage.com to 21 Apr. [Internet] Nice flap shot in the rear view too.
flap snot (n.) [snot n.1 (4)]

vaginal secretions.

J. Morgan on MessedUp.net [Internet] Puss Juice: Bitch Butter, clam jam, crotch oil, fanny batter, flap snot, French Dip, goose grease, crotch gravy, love juice.

SE in slang uses

In phrases