Green’s Dictionary of Slang

AC/DC adj.

also AC-DC
[the opposite varieties (alternating and direct) of electrical current]

1. (also AC and DC) bisexual; usu. of a person but note cit. 1979.

[US] (ref. to late 19C) N. Kimball Amer. Madam (1981) 237: Some of the lavender group used to come to my house; those were the bi-sexual ones. Later the joke was they were AC and DC like the electric currents.
[US]Wentworth & Flexner DAS 1/2: ac-dc ac/dc adj. Bisexual. Some jocular use since c.1940.
[US]S. Longstreet Flesh Peddlers (1964) 303: Her callow outlook on things was ready for any seduction. Double gaited, wired for A.C. or D.C.
[US]M. Spillane Return of the Hood 65: I don’t trust any of those AC-DC guys.
[Aus]B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 35: Why didn’t you say you were A.C./D.C.
[US]L. Bangs Psychotic Reactions (1988) 137: Bisexual . . . what’s that other word, AC/DC?
[US]E. Torres After Hours 164: She started out in one of his deluxe ac/dc cathouses.
[UK]P.D. James Innocent Blood (1981) 41: He’s AC/DC by the way.
[UK](con. late 1960s) P. Bailey An Eng. Madam 83: AC/DC couple seek similar for foursomes.
[Aus]G. Seal Lingo 114: Bisexuality (ac-dc) and terms for lesbians (dike, lezzo, butch) are well outnumbered by the terms for male homosexuality. While gay has become the accepted mainstream term, the vernacular is still full of other, less positive terms.
[UK]M. Manning Get Your Cock Out 31: The cloakroom boy [...] pushed his luck and asked dandy to fist him. Dandy obliged the cheeky little AC/DC horn smoker.

2. (gay) happy to take either the active or the passive sexual role.

[US]J. Stanley ‘Homosexual Sl.’ in AS XLV:1–2 55: AC-DC adj [...] 2: Ambivalent in the active or passive roles of a homosexual relationship.
[US]R.O. Scott Gay Sl. Dict. [Internet] AC-DC: [...]. 3. a homosexual who is able to fuck or be fucked.