backyard, n. — Green’s Dictionary of Slang

backyard n.

(US) the buttocks, esp. in the context of anal intercourse.

1966		Trimble 5000 Adult Sex Words and Phrases 21: back yard (Vulg.) n. The Anal region of the Buttocks, particularly to a Sodomite.
1972		R.A. Wilson Playboy’s Book of Forbidden Words.
1989–2003		R.O. Scott Gay Sl. Dict. 🌐 back yard: the buttocks.
1995		Francis-Jackson Official Dancehall Dict. 2: Back-yard buttocks: u. ’ar backyard ’eavy/she has a well padded behind.
2004		S. Stukin in Vibe (Boulder, CO) Mar. 142/2: [C]elebrities like Beyoncé and J.Lo are as famous for their bangin’ backyards as they are for their God-given talents.

backyard cousin (n.) (also backyard relation)

(US) a relation, poss. an illegitimate child, of whom the speaker is not proud.

1940		H.W. Thompson Body, Boots and Britches 498: He’s a backyard relation: (their cat came over into our yard once).
1983		in DARE I 125/1: backyard cousin — Heard from an 81-year-old woman who didn’t specifiy illegitimacy. She said, ‘A backyard cousin is somebody you’re not especially proud to own.’.

backyard trots (n.) [trots n. (1); one also ‘trots’ through the back door on the way to the privy]

(US) diarrhoea.

1965–70

backyard telephone booth (n.) [its position and size; telephone n. (2)]

(US) a privy.

1965–70