1(colloquial) To lose one's temper; to snap or blow up (emotionally).
彼はちょっとしたことでよくキレるから、扱いが難しい。
He often snaps over small things, so he's hard to handle.
渋滞でイライラして運転手がキレてしまった。
The driver lost his temper because of the traffic jam.
SNSで誹謗中傷されて、ついキレて反論してしまった。
I was slandered on social media and ended up snapping back in reply.
上司に理不尽に叱られて、彼女はついキレる寸前だった。
Being unfairly scolded by her boss, she was about to lose her temper.