Green’s Dictionary of Slang

(Aus.) of a woman, to make oneself available for sex with a number of men in sequence.

1985

Tracks (Aus.) Oct. 82: One roots, one gives head [i.e., fellates] and the other gangies [?makes herself available for a gang-bang — i.e., where several males have sexual intercourse seriatim with one female] [Moore 1993].