A sack-tap is a light tap (it hurts tho!) that a fellow soccer player may do to another player, where a dude raps the sac-de-noix of another guy.
I sack-tapped Matt, and now he's got everyone trying to sack-rap me!
A trick played on a fellow athlete where the open hand smacks the target's testicles with the knuckles in a sharp, wrist flicking motion.
"Dude, I sack tapped Brandon, and now he has the whole team trying to sack tap me"
The sudden and random striking of a person's cock and balls with slight wrist action.
I sack tapped him so hard today that he fell down on the ground.
an action Steven Crowder asks you to do to him because he's totally not gay.
Steven Crowder : Hey you must Sack Tap me and keep it between us ;)
Male staffer : What the fuck
A form of play-fighting in which male friends gently tap each other on their testicles, not to injure, but to playfully tease each other for mutual amusement.
"Boys will be boys."
"What you mean?"
"Your boyfriend just gave mine a sack tap."
"Oh! Ha! I missed it. Boys will be boys..."
By far one of the gayest things you can do as a male.
Walking up, and touching another dude in the balls. Your gay. No way around it. Sack Tapping is for the gays.