noun, noun or participle which takes 'suru'
really pissed off; seriously angry; losing it for real
Slang term for genuine, intense anger, as opposed to just being annoyed. Often used when someone finally snaps after holding back.
See also: キレる
あの先生、ついにマジ切れしたらしいよ。
I heard that teacher finally snapped for real.
冗談のつもりだったのに、彼がマジ切れして怖かった。
I was just joking, but he got seriously angry and it was scary.