Green’s Dictionary of Slang

1. (US black) a woman who permits sexual intimacy but refuses intercourse; or anyone who prevents others from pursuing sexual relations.

1980		E.A. Folb Runnin’ down some Lines.
1990		R.A. Spears Forbidden Amer. Engl. 38: ‘‘Man, you do a cock-block like that on me again, and your ass is grass’ [Simes:DLSS].
1999		Eble Campus Sl. Apr. 2: cockblock – interfere with or prevent two people from pursuing intimate relations: ‘He really cockblocked me last night.’ Also a noun, one who cockblocks.
2000		Ebonics Primer at www.dolemite.com 🌐 cock block Definition: female who fucks around to the point of intercourse and stops Example: I was chillin at this party when dis young cock block bitch licked once and left.

2. (UK black) a male who interferes with another male's sexual advances.

2016

A. Wheatle Crongton Knights 180: ‘You fat ass has been in the way [...] Stop being a cock-block!’.