The bunching effect that takes place when the sweat from a good workout meets the boxers in the grundle region. Also can be used as an insult.
Man I need to hit the showers I've got Grundlebundle like nobody's business.
or
Man that clerk always thinks im trying to steal , what a grundlebundle.
When one man is in the downward dog position, another man approaches from the rear in a crab walk inserting each other’s penises into the reciprocating anus, while relocating testicles to one side allowing for maximum grundle on grundle contact.
Hey man, the wife ran to the grocery. Think we got time for a double grundle bundle?
Another name for a mans cock and balls, or...
When a gay orgy is in progress one takes a handfull of a mans section between his anus and balls and bites it.