lose one's cool
see under keep one's cool.
cool story, bro
Read more in this article about some frequently asked questions and fun facts related to our definitions.
Loose vs. Lose
Did you lose that sock in the dryer ... or loose it?
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.