Green’s Dictionary of Slang

prong v.

[prong n. (1)]

1. to have sexual intercourse.

[US] in E. Cray Erotic Muse (1992) 211: He claimed he could prong more cunts with his dong / Than Ivan Skavinsky Skavar.
[US] in G. Legman Limerick (1953) 55: She went down on the gents, / And pronged the girls’ vents / With a clitoris reaching six inches.
[US](con. 1940s) E. Thompson Tattoo (1977) 116: Who the hell could have told Brother Dub he had pronged his mother?
[Aus]D. Maitland Breaking Out 144: Compromising cows, pronging pigs and other gross offences of a bestial nature.
[Aus]J. Clanchy Lie of Land 229: Dear Gloria, I’ve wronged yer / shouldn’t have pronged yer.

2. (US black) to enjoy oneself [poss. euph. for sense 1].

[US]M.H. Boulware Jive and Sl.

3. (US gay) to have anal intercourse.

[US]G. Indiana Rent Boy 72: I’m pronging him with my torso arched back.