adjective

of or at a fairly low temperature.

it’ll be a cool afternoon

chilly,cold,fresh,crisp,refreshing,invigorating,bracing,brisk,unheated,draughty,nippy,parky,chill

noun

a fairly low temperature.

the cool of the night air

chill,chilliness,coldness,coolness,freshness,crispness

verb

become or make less hot.

we dived into the river to cool off

chill,refrigerate,make cold/colder,get cold/colder,cool down,lose heat