Green’s Dictionary of Slang

1. to be a bisexual.

[1654		Mercurius Fumigosus 24 8–15 Nov. 206: Yet she seems oth’ doubtfull Gender to me. / Though her Habit and Actions either way leane].
1969		B. Jackson Thief’s Primer 173: She’s [i.e. a male homosexual] got a bunch of them in the tank with her that are going both ways.
1972		C. Bukowski Erections, Ejaculations etc. 140: The guy went both ways – I mean he fucked men and women and was fucked by men and women.
1999		Dr Dre ‘XXplosive’ 🎵 Bet you didn’t know she goes both ways.
2000		C. Cook Robbers (2001) 315: Maybe you flip both ways. Maybe you get off on rough trade, too.
2023		R. Milward Man-Eating Typewriter 4: Espresso-schlumphing, pâté-nibbling, jibbering, both-way-swinging [etc].

2. to take either role in sado-masochistic sex.

1970		L. Sanders Anderson Tapes 97: D’MEDICO: [I] found out he was bent, sex-wise [...] Whips. ANGELO: Which way is he? This is important. D’MEDICO: Both ways, from what I hear.
1979		J. Rechy Rushes (1981) 99: ‘You see the earring? Left side! And the handkerchief? All on the left side, man! That means top-man, man. Top!’ ‘Some guys go both ways, stud. No offense.’.