slang To be calm and composed, especially in times of stress. I was petrified to take the stage, but Alice was as cool as a cucumber.Practicing meditation has helped me to be as cool as a cucumber in times of trouble.
extremely calm; imperturbable. (*Also: as ~.) Joan felt nervous, but she acted as cool as a cucumber.The politician kept cool as a cucumber throughout the interview with the aggressive journalist.
to be very calm and relaxed, especially in a difficult situation I expected him to be all nervous before his interview but he was as cool as a cucumber.
Calm and composed, self-possessed, as in Despite the mishap Margaret was cool as a cucumber. This idiom may be based on the fact that in hot weather the inside of cucumbers remains cooler than the air. [c. 1600] For a synonym, see cool, calm, and collected.