trillsack Share definition Flag One who third wheels or is a cock blocker. Usually associated with someone that has bitch tits or a small penis Guy 1: You get any last night? Guy2: No, that trillsack ruined everything. trillsack by trillsackheadshot October 25, 2009 0 0 Get merch Get the trillsack mug. Buy Now — $32.95 See more merch