The 375ml bottle of liquor available for purchase. It is small enough to fit in your back pocket, aka your ass pocket.
Guy: I'm halfway through my ass pocket of Jack daniels
Girl: What is an ass pocket?
Guy: 375ml of liquor, it fits in your ass pocket.
Girl: Well it's not on UrbanDictionary.
Guy: It is now.
A fifth (200 ml) flat bottle of liquor. So named because it easily slides into the ass pocket. Immortalized on blues legend RL Burnsides' "A Ass Pocket of Whiskey"
Yo, I got an ass pocket of Jameson's, imma go sit under a bridge and get fookin ripped.
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.