An extra sack of skin found between the Genitals and Asshole occurring as an anomaly in about 1 in every 100 people.
Lick my Butt-sack!
Damn, I just sat on my Butt-sack!
When you bend over with no pants or underwear on, and from behind, it looks like your butt has a ball sack.
(this takes place in a locker room)
Man 1: "Dangit, i dropped my deodorant."
(man 1 bends over naked to pick it up)
Man 2: "What?"
(man 2 looks over to see what happened)
Man 2:"DUDE!, i can see your butt-sack!