Green’s Dictionary of Slang

(UK black) the rubbing of one’s body, esp. the genital area, against one’s partner while dancing.

1999		(con. 1979–80) A. Wheatle Brixton Rock (2004) 76: Nuff steaks go der, and any man [...] is guaranteed a crub if he ain’t too ugly.
2001		A. Wheatle East of Acre Lane 2: I was riding a serious crub wid a fit girl.