Cap worn whilst balling
What up, Captain that's one helluva a ball cap you're wearin??
Similar to the teabag, in this instance, the male places his genitals on top of the head of a female partner, (or a friend to be embarrassed). The balls rest on their head as if they were a cap, the penis of course is the Bill of the Ball Cap.
That asshole went out on a date with my sister, I came home and they were watching TV on my couch so i just gave him a ball cap.