your nutsack more back than normal touching your asshole causing major rashing when shiting
His huge buttsac gave a rash all the way down his leg after relieving his massive shit!
A sac used to hold one's saggy butt (usually caused by being a buttslut).
Jas has a buttsac the size of a parachute.
Jas sometimes has to use 2 buttsacs, double wrap.