A two litre bottle of cheap cider, which is consumed mostly by unemployed youths. It is generally a bottle of Strongbow, although Woodpecker and Pulse are other common brands, Pulse being the cheapest.
Guy1: "Hey man, are you going to that party on saturday?"
Guy2: "Yeah man, wouldn't miss a pissup"
Guy1: "What you drinking?"
Guy2: "Well i'm an unemployed youth, so i'll probably just get a 2 bomb."
Guy1: "Dude, cider's nasty. I'm getting buckfast."