Green’s Dictionary of Slang

1. a bout of quick sexual intercourse.

1960		(con. WWII) G. Sire Deathmakers 198: I’d like to have a quick dip.
1976		D. Ireland Glass Canoe (1982) 188: Her sister was a cheap prostitute in the pub where she worked — you know, a quick dip upstairs, then minutes later she’d be down serving beer in the bar.

2. (US prison) one who participates in anal intercourse.

1977

P. Hamill Flesh and Blood (1978) 32: You are what is known as a white fuck. A white fuck don’t do easy time. You can be a duke or a dip, a fuck boy or a jailhouse punk.