cooler Syllabification: (cool·er)Pronunciation: /ˈko͞olər/Definition of cooler noun 1an insulated container for keeping food and drink cool. a refrigerated room. 2a tall drink, especially a mixture of wine, fruit juice, and soda water. 3 (the cooler) informal prison or a prison cell. cooler in other Oxford dictionaries Definition of cooler in the British & World English dictionary