(verb) to lose control of your emotions
The poor schoolteacher flipped out and started crying when she won five million dollars in the lottery.
The workers complained to their boss because the manager was always flipping out over unimportant things.
Boyfriend: We need to talk.
Boyfriend: Please don’t flip out, but I think we should date other people.
Girlfriend: What?! I thought we were going to get married! I hate you!
Boyfriend: I asked you not to flip out!