To become cooler, to be reduced in temperature.(verb)
To cause the temperature of an item to decrease.(verb)
To become less agitated.(verb)
To cause to become less agitated.(verb)
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Use "cool down" in a sentence
"Fans moved in synchronized rhythm either to the beat of the fast-paced, hallelujah-shouting music or to cool down the sweat of the “private summers” the young fifty-something women had found themselves entrenched in."
"The plane stopped alongside the airstairs at the entry to the hangar, its nose section poking into the actual hangar it had to cool down outside for a few hours before it could be brought fully inside for storage."
"Cleansed, scented, hair wet and cool down the length of my spine, I feel like a goddess, jailed in her Olympus."