A bag (preferably brown paper bags) that you bring to a given place or event when you know you're gonna vomit.
Kennedi: if you're gonna yak, please don't do it on the seats of the car
Carly: don't worry I brought my yak sack!
Carly: don't worry I brought my yak sack!
by CHARLITTTTTTTTTTT September 15, 2017

by Americaferlyfe120 June 01, 2011

by BAFNEQUE November 15, 2009
