1. The quality of remaining calm, composed, and rational in stressful or emergency situations; the ability to think clearly under pressure
The doctor's coolheadedness during the emergency saved the patient's life.
A serenidade do médico durante a emergência salvou a vida do paciente.
2. Lack of emotional reactivity; maintaining mental clarity despite provocation or difficulty
His coolheadedness in negotiations made him an excellent diplomat.
Sua serenidade nas negociações o tornou um excelente diplomata.