Perfectly composed; self-possessed

The defendant sat through the entire murder trial as cool as a cucumber, as if it wasn't a matter of life and death for him

L'imputato di omicidio è rimasto impassibile per tutto il processo, come se la cosa non lo riguardasse affatto

He'll make a great firefighter because even in the most difficult situations he keeps his cool and stays cool, calm and collected

Sarà un ottimo vigile del fuoco perché anche nelle situazioni più difficili è sempre padrone di sé e riesce a mantenere una calma olimpica

The cool temperature of cucumbers was observed long ago, and now it has been proved that on a warm day the inside of a cut cucumber is 20 degrees cooler than the outside air