Wiktionary
lose one's temper
vb. (context intransitive idiomatic English) To become explosively angry or very cross.
WordNet
lose one's temper
v. get very angry and fly into a rage; "The professor combusted when the student didn't know the answer to a very elementary question"; "Spam makes me go ballistic" [syn: flip one's lid, blow up, throw a fit, hit the roof, hit the ceiling, have kittens, have a fit, combust, blow one's stack, fly off the handle, flip one's wig, blow a fuse, go ballistic]
Usage examples of "lose one's temper".
Every so often it was good to lose one's temper, and Presidents were allowed.
But it is sometimes as difficult to lose one's temper as it is difficult at other times to keep it.