keep one's cool

keep one's cool idiom
Retain one's composure and poise, as in Billy keeps his cool, no matter what the situation. This slangy usage dates from the mid-1900s, as do the antonyms blow one's cool and lose one's cool, as in Try not to blow your cool in front of the team, or Dad lost his cool when he saw Jim playing with matches. Also see keep cool.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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