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.
Words nearby cool as a cucumber
cooktop,
cooktown orchid,
cookware,
cooky,
cool,
cool as a cucumber,
cool bag,
cool down,
cool drink,
cool hunter,
cool it