Guillosack Share definition Flag Having one's sack injured by, and not limited to, a chopping, pinching, slashing motion. Much like a guillotine would. The weed-whacker's chain inched closer to his leg and guillosacked an unsuspecting Dylan. Guillosack by CMin8her May 31, 2010 0 0 Get merch Get the Guillosack mug. Buy Now — $32.95 See more merch