What is BM in League of Legends? [duplicate]
Solution 1:
BM stands for Bad Move/Manner/Mouth.
This term isn't exclusive to LoL and is used in quite a few games such as Hearthstone, Overwatch and just about any competitive game.
It's basically when you are being a jerk unnecessarily to someone. e.g "T-bagging" someone, leaving someone on 1 HP just to kill them anyway, taunting, etc.