1. (noun) An old backpack you have that used to be your backpack for school 4 years ago, but since you got a new one, it is used only for transporting beer or other alcoholic beverages. Used by many people who walk places to go drink and can't afford the money for a cab and don't have a friend willing to drive them.
1. Dude this was my school backpack during 7th grade but now since I got a new one, this is my designated beer pack.
a backpack designed specifically to transport beer.
I guess you should have brought a beerpack to the store with you to carry the 2 below.