yack star Share definition Flag A person who throws up after getting wrecked, usually at a party or on a party bus Rita was upset that her boyfriend broke up with her so she downed a bottle of Bacardi while on a party bus and became the lone yack star, ruining the bus for everyone else yack star by yaboiwill January 16, 2014 0 0 Get merch Get the yack star mug. Buy Now — $32.95 See more merch