Green’s Dictionary of Slang

1. (US black) to have sexual intercourse.

1994

G. Smitherman Black Talk.

2. (Aus.) to subject a woman, voluntarily or otherwise, to intercourse with multiple males.

1975		T. Blake Fig Tree 13: Aussie mateship, mate. You don’t dob your mates. And what better mate than one who’d bunned his sheila for you? [Simes:DLSS].
1998		R.G. Barrett Mud Crab Boogie (2013) [ebook] The boys were in there bunning Warren’s girl.