When a male human uses his penis to slap someone. Usually done at full length, but not completely stiff to allow for a whipping action. Commonly used against passed out victums. (Can be slightly painful for the slapper, but the comic effect is usually worth it)
Did you get cock slapped last night? You have a mushroom bruise on your cheek.
If you don't shut up I am gonna cock slap you in your sleep.