Balloon knot spot
Much like a blood spot that a woman gets on her pants during her period, the balloon knot spot is when a man's ass begins to bleed after too much anal sex and a blood spot is visible through his pants around his anus.
Steve: Hey Lance, you better change your pants again.
Lance: Why, did I poop myself again?
Steve: Nope, you've got yourself a balloon knot spot!
Lance: Why, did I poop myself again?
Steve: Nope, you've got yourself a balloon knot spot!