when one bro slaps another bro in the face with seamen while one bro is vulnerable such as while he is sleeping, jerkin the gerkin, or drunk out of his mind.
Yo last night Chad was gettin it on with Sally and i came up behind him and wet slaped that bitch
When a girl gives a hand-job to a guy and then slaps his face with his cum still in her hand, spreading it all over his face - as a part of women's retaliation for all the nasty sexual things men do to them so they can tell their friends later (or write about it on urban dictionary...).
"He acted like such a douche last night I had to wet-slap him. He got the wet slap alright."