(US black) the mouth, esp. as used in oral-genital sex; thus in phr. give (someone) some cap, to fellate, to perform cunnilingus.
|‘The Fall’ in Life (1976) 83: For lick and a lap from her mellow cap / The trick would fight a duel.et al.|
|Jailhouse Jargon and Street Sl. [unpub. ms.].|