A child, usually named Callum, or Cal, that looks like a school shooter. Signs of being a callumbine range from sitting alone in a corner every lesson and break, and watching many videos containing guns.
Girl1: "what's up with Cal over there?"
Girl2: "I don't know, but I think he's becoming a bit of a Callumbine..."
Girl2: "I don't know, but I think he's becoming a bit of a Callumbine..."
by Curious peach December 13, 2016
Get the Callumbinemug.