Green’s Dictionary of Slang

flap n.1

1. [mid-17C; 1910s+] (also flaps) a promiscuous woman; a prostitute.

2. [late 18C–1920s] any garment that has a pendant flap or flaps.

3. [late 19C] (UK Und.) strips of lead used on roofs.

4. [late 19C–1910s] the vagina.

5. [late 19C+] (also hearing flap, side-flap) an ear, usu. large.

6. [late 19C+] in pl., the labia majora.

7. [1950s+] (US) the mouth.

8. [1950s+] (Aus.) a cheque.

In compounds

flap-cap (n.)

[early 18C] a whore.

flap shot (n.) [SE shot, a picture]

[1970s+] in pornographic still or moving pictures, a close-up shot of the labia and open vagina.

flaptabs (n.) [tab n.1 ]

[1950s+] the ears.

SE in slang uses

In phrases