A bunker is when you sneak up behind a player and shoot them at close range in paintball. This usualy leaves the best bruises as the paint sphere most of the time does not explode!
guy 1: There's a cliff ahead and my breaks don't work!
guy 2: BUNKER man
guy 1: i know!
Guy 3: did u hear about Chet and Bret going off that cliff?
Guy 4: yeah, now where R we gunna get our weed man?
Guy 3: I know, it's pretty BUNKER huh?