Green’s Dictionary of Slang

(Aus.) of a man, to be one of the last to participate in the multiple rape of or intercourse with a woman.

1979		Lette & Carey Puberty Blues 76: Steve Strachan arrived late. ‘I’m not goin’ fuckin slops.’.
1985		‘Thommo’ Dict. Aus. Swearing & Sex Sayings 60: GOIN’ SLOPS — To have sexual intercourse with a female, straight after one or more of your mates have ejaculated semen into her vagina.
1990		Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Slops. To be a late participant in a gang rape. As in ‘to go slops’.