Hitting or crushing an unsuspecting bellend, or willy, with a large object to cause comparable, or greater, pain to a sack tap.
Guy 1: Ouch! WHAT THE HELL?
Guy 2: Ha, got ya! That's called a sack tap.
Guy 1: You got my bloody dick!
Guy 2: Oh, well we'll call that a bellend buster.

Guy 1: F you! *crouching in pain*
by voss4life June 19, 2015
Get the bellend buster mug.