Green’s Dictionary of Slang

chop-up n.2

[chop v.5 (1)]

(Aus.) an act of group sex by multiple men and a single woman; whether voluntary or coerced.

[Aus]R.G. Barrett Mud Crab Boogie (2013) [ebook] ‘Wouldn’t go in there?’ Norton’s brow furrowed. ‘Why not?’ ‘The boys have got a chop-up going’.