slop, v. — Green’s Dictionary of Slang

slop v.

[SE slop, to feed an animal with slops]

1. (Aus.) in fig. use, to feed, to give, to apportion.

1902

Bulletin (Sydney) 20 Dec. 26/4: The law decided that [...] the co-respondent did commit adultery – at least the law joyfully ‘slopped’ the co-re. in costs and other woes.

2. (UK black) to fellate.

2017

Unknown T ‘Bop with Smoke’ 🎵 Oi, this fucking uck is immense / The way that she slop on the top, issa mess.

In phrases

slop at the hog trough (v.)

(US black) to perform cunnilingus.

1988

(con. 1930s) C.E. Lincoln The Avenue, Clayton City (1996) 17: The man who was suspected of oral sex was accused of ‘slopping at the hog trough’.