cool ‧ er /ˈkuːlə $ -ər/ BrE AmE noun [countable]
[ Word Family: noun : ↑ cool , ↑ coolness , ↑ cooler , ↑ coolant ; verb : ↑ cool ; adverb : ↑ coolly ; adjective : ↑ cool ]
1 . a container in which something, especially drinks, is cooled or kept cold:
Mike went to fetch a bottle of wine from the cooler.
2 . American English a coolbox
3 . American English a machine that provides ↑ air conditioning
4 . the cooler informal prison