oink, n. — Green’s Dictionary of Slang

oink n.

[oink, onomat. for a pig’s grunt, var. on pig n. (2a)]

1. (orig. US black) a police officer.

1970		C. Major Dict. Afro-Amer. Sl. n.p.: Oink:...a cop; policeman; law-enforcement officer.
1980		D. Hamill Stomping Ground 183: You and the rest of your oink friends [HDAS].
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 129/1: oink oink n. 2 a police officer.

2. (N.Z. prison) a skinhead.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 129/1: oink oink n. 1 a skinhead.