look up any word, like blumpkin:
 
1.
A womans chin used for resting a mans scrotum while recieving oral pleasure
Mind if I come over and use your sack warmer for a couple of hours?
by mooseknuckles November 13, 2002
 
2.
The act of warming ones balls by releasing flatulence within confined clothing
Yo man, my nutz were cold until I floated a sack warmer.
by The Napalm Overlord April 03, 2014