Meaning of the word "as cool as a cucumber" in English

What does "as cool as a cucumber" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

as cool as a cucumber

US /æz kuːl æz ə ˈkjuːkʌmbər/
UK /æz kuːl æz ə ˈkjuːkʌmbər/

Idiom

very calm and composed, especially in a difficult or stressful situation

Example:
Even when the building was on fire, the firefighter remained as cool as a cucumber.
She walked into the interview as cool as a cucumber, despite her nerves.