lose one's cool

present singular third person loses one's cool · participle present losing one's cool · participle past lost one's cool · past lost one's cool

1. idiomaticTo become upset or disconcerted; to lose one's temper.

   The fiery femme fatale is notorious for losing her cool, and was once accused of hitting her secretary with a telephone and threatening to throw her from a moving car.

   2006 April 28, Stefanie Cohen, “Naomi Campbell Accused of Attacking Maid in Fit Over Jeans”, in FOXNews.com, retrieved 03 Jun 2009

   1 more example

   But in his final singles match against Mandarino, the Menace lost his cool. Visibly rattled by noisy spectators, who chanted "Brasil! Bra-sil!" from the third set onward, he collapsed completely in the fifth set.

   1966 November 18, “To the Ludicrous”, in Time

   Synonyms: blow one's cool, blow one's top, drop one's bundle, go ape, go apeshit, hit the roof, hit the ceiling, lose it · Antonyms: keep one's cool