cool / koōl/ • adj. 1. of or at a fairly low temperature. ∎  soothing or refreshing because of its low temperature: a cool drink fig. the bathroom was all cool, muted blues. ∎  (esp. of clothing) keeping one from becoming too hot: cool, comfortable shirts. ∎  showing no friendliness toward a person or enthusiasm for an idea or project: he gave a cool reception to the suggestion. ∎  free from excitement or anxiety: he prided himself on keeping a cool head. ∎  calmly audacious: such an expensive strategy requires cool nerves. ∎  (of jazz, esp. modern jazz) restrained and relaxed.2. inf. fashionably attractive or impressive: I always wore sunglasses to look cool. ∎  excellent: [as interj.] a computer you didn't even have to plug in. Cool! 3. (a cool ——) inf. used to emphasize a specified quantity or amount, esp. of money: a cool $15,000 to buy the franchise.• n. 1. (the cool) a fairly low temperature: the cool of the night air. ∎  a time or place at which the temperature is pleasantly low: the cool of the evening. ∎  calmness; composure.2. the quality of being fashionably attractive or impressive: all the cool of high fashion.• v. become or cause to become less hot: [intr.] we dived into the river to cool off | fig. his feelings for her took a long time to cool | [tr.] cool the pastry for five minutes. ∎  become or cause to become calm or less excited: [intr.] after I'd cooled off, I realized I was being irrational | [tr.] George was trying to cool him down. ∎  [usu. in imper.] (cool it) inf. behave in a less excitable manner: “Cool it and tell me why you're so ecstatic.”PHRASES: cool one's heels be kept waiting.keep (or lose) one's cool inf. maintain (or fail to maintain) a calm and controlled attitude.play it coolsee play.DERIVATIVES: cooled adj. cool·ish adj.cool·ly adv.cool·ness n.

cool adj. OE. cōl = MLG., MDu. kōl (Du. koel) :- Gmc. *kōluz, f. *kōl- *kal- (see COLD); as sb. from XIV.
Hence cool vb. OE. cōlian = OS. cōlon :- Gmc. *kōlōjan, f. *kōluz.

cool cool as a cucumber completely calm; the term is recorded from the mid 18th century.
Cool Britannia Britain, perceived as a stylish and fashionable place; especially (in the late 1990s) as represented by the international success of and interest in contemporary British art, popular music, film, and fashion.