cool down phr v 1 [I, T cool sth ↔ down] to become a little colder, or to make something a little colder （使）变凉，（使）冷却下来: Let the engine cool down. 让发动机冷却下来。 2 [I] to become calm after being angry 〔生气后〕冷静下来: The long walk home helped me cool down. 长途步行回家帮助我冷静下来。