An exceptionally large scrotum.
DAMN!!!!! DAT fool's got a FAT SAC!!!!
by fun-o-bunz August 13, 2003
a large sac of marijuana.
"Let me buy that fat sac off you."
by tha dude December 17, 2006
Its a sac of fat that is someplace on your body you don't want it
you're a fatsac
by The gr 6 class of holy name May 28, 2011