Green’s Dictionary of Slang

1. to have sexual intercourse, orig. of a man; to behave in a sexually provocative way [his ‘mounting’ of his partner].

1933		R. Chandler ‘Blackmailers Don’t Shoot’ in Red Wind (1946) 107: You Hollywood frails must be hard to get on with.
1941		in G. Legman Limerick (1953) 22: There’s an unbroken babe from Toronto, / Exceedingly hard to get onto.
1953		S. Bellow Augie March (1996) 128: I didn’t ask her age before getting on her.
1969		B. Jackson Thief’s Primer 40: And this other one, the one that had already fucked him, he held him down while this other boy was getting on. And that’s when the boss come up there and caught them.
1971		L. Sanders Pleasures of Helen 246: ‘I get off at midnight,’ the cop said. ‘May be,’ she said shrewdly, ‘but son, you ain’t getting on at midnight’.
1982		P. Barker Union Street 189: When she come back she got on with Ted, and married him.
1997–2001		Online Sl. Dict. 🌐 get on v 1. to have sex. (‘She got on that guy last night.’) 2. to kiss passionately; MAKE OUT. (‘She got on that guy last night.’) Note: extremely ambiguous term.
2006		R. Antoni Carnival 174: I ran into Poison, the band famous for all the wild young girls.Their scandalous bikini-mas. Coolie Caravan was the DJ on their big truck – blasting Denyse Plummer’s ‘Get on Bad’ – and let me tell you the young girls were doing just that.

2. to physically attack.

1889		Dead Bird (Sydney) 9 Nov. 6/4: Burge [...] has not nearly the skill of Poqwell, but when he ‘gets on’ his blows tell.
1927		T.A. Dorgan in Zwilling TAD Lex. (1993) 105: Benny Leonard then got on with Walsh for his third try.
1973		C. Gaines Stay Hungry 126: I’m gonna get on that motha [...] I’m gonna get on that bastard like baby doo on a wool blanket.