BG may refer to any of the following:
1. BG is shorthand used to describe a bad game. Typing this in chat lets other players in the game know you thought the game was no fun, often because the game is imbalanced.
4. Short for battleground, BG is a place where people meet online to fight or battle.
5. BG is an acronym for the game Baulder's Gate.
6. BG is chat slang for big grin.