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.