Green’s Dictionary of Slang

(US) the buttocks, the anus.

1967		P. Thomas Down These Mean Streets (1970) 6: ‘Go to bed son,’ Poppa said, playfully kicking me in the culo.
1972		B. Rodgers Queens’ Vernacular.
1987		NWA ‘Dopeman’ 🎵 But if she happens to die, because of your drug / I’m puttin' in your culo, a .38 slug!
1990		S. Morgan Homeboy 326: Smoke [...] That’s all Aldo was blowing up your culo.
1993		A. Rodriguez Spidertown (1994) 152: lookit that’ culo, bro’, jus’ lookit!
2000		R. Antoni Grandmother’s Erotic Folktales 120: You poor mummy gets that look on she face red red like she’s trying to make a caca with a corcho inside she culo!
2012		J. Díaz This Is How You Lose Her 149: How skinny she was, no culo, no titties.
2019		D. Winslow Border [ebook] ‘You want my culo?’.