Cool down definition: If someone cools down or if you cool them down , they become less angry than they were. Cooldown definition, a period of low-impact or slower exercise following a more intense workout to allow the body to gradually return to its normal physiological level. Cooldown definition is - the act or an instance of allowing physiological activity to return to normal gradually after strenuous exercise by engaging in less strenuous exercise. | Meaning, pronunciation, translations and examples See more.