When a girl is giving you head and your nut sack slaps her chin, nose or cheek (depending on position), usually after a most-aggressive head bobbing.
Mary gave me a bj last night and she went down so hard she got a sack slap from me also.
When a male person rubs their hand across their nut sack
and slaps someone in the face with it.
Mike: I heard Raul took your juice box.
Taiquan: If he did, he's gonna get a sack slap to the face.
Mike: That shit sucks.
n. a sharp tapping sound made with a man's testicles. usually against their partner's ass during intercourse. This is also valid against one's chin.
my girlfriend really enjoys it when my balls sackslap her booty during sex.
1) The act of rubbbing the sweat off of your own testicals and proceeding to smack the nearest individual in the face
2) when one man randomly decides to smack a mans ballsack in the middle of Lunch
TIM- Ahh what was that for, man?
HENRY- Dude, You just got sack slapped!