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adjective, cool·er, cool·est.
  1. moderately cold; neither warm nor cold: a rather cool evening.
  2. feeling comfortably or moderately cold: I'm perfectly cool, but open the window if you feel hot.
  3. imparting a sensation of moderate coldness or comfortable freedom from heat: a cool breeze.
  4. permitting such a sensation: a cool dress.
  5. not excited; calm; composed; under control: to remain cool in the face of disaster.
  6. not hasty; deliberate: a cool and calculated action.
  7. lacking in interest or enthusiasm: a cool reply to an invitation.
  8. lacking in warmth or cordiality: a cool reception.
  9. calmly audacious or impudent: a cool lie.
  10. aloof or unresponsive; indifferent: He was cool to her passionate advances.
  11. unaffected by emotions; disinterested; dispassionate: She made a cool appraisal of all the issues in the dispute.
  12. Informal. (of a number or sum) without exaggeration or qualification: a cool million dollars.
  13. (of colors) with green, blue, or violet predominating.
  14. Slang.
    1. great; fine; excellent: a real cool comic.
    2. characterized by great facility; highly skilled or clever: cool maneuvers on the parallel bars.
    3. socially adept: It's not cool to arrive at a party too early.
    4. acceptable; satisfactory; okay: If you want to stay late, that's cool.
  1. Informal. coolly.
  1. Slang.
    1. (used to express acceptance): Okay, cool! I'll be there at 10:00.
    2. (used to express approval, admiration, etc.): He got the job? Cool!
  1. something that is cool; a cool part, place, time, etc.: in the cool of the evening.
  2. coolness.
  3. calmness; composure; poise: an executive noted for maintaining her cool under pressure.
verb (used without object)
  1. to become cool (sometimes followed by down or off): The soup cooled in five minutes. We cooled off in the mountain stream.
  2. to become less ardent, cordial, etc.; become moderate.
verb (used with object)
  1. to make cool; impart a sensation of coolness to.
  2. to lessen the ardor or intensity of; allay; calm; moderate: Disappointment cooled his early zealousness.
Verb Phrases
  1. cool down, to bring the body back to its normal physiological level after fast, vigorous exercise or activity by gradually slowing the pace of activity or by doing gentle exercises or stretches.
  2. cool off, Informal. to become calmer or more reasonable: Wait until he cools off before you talk to him again.
  3. cool out, Slang. to calm or settle down; relax: cooling out at the beach.
  1. blow one's cool. blow2(def 44).
  2. cool it, Slang. calm down; take it easy.
  3. cool one's heels. heel1(def 26).

Origin of cool

before 1000; Middle English cole, Old English cōl; cognate with Middle Low German kōl, Old High German kuoli (German kuhl). See cold, chill
Related formscool·ing·ly, adverbcool·ish, adjectivecool·ly, adverbcool·ness, nouno·ver·cool, adjectiveo·ver·cool·ly, adverbo·ver·cool·ness, nounre·cool, verbsub·cool, verb (used with object)ul·tra·cool, adjectiveun·cooled, adjectivewell-cooled, adjective

Synonyms for cool

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Synonym study

1. See cold. 5. See calm.

Antonyms for cool

1, 3, 4, 7, 8. warm. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for cool

Contemporary Examples of cool

Historical Examples of cool

British Dictionary definitions for cool


  1. moderately colda cool day
  2. comfortably free of heata cool room
  3. producing a pleasant feeling of coldnessa cool shirt
  4. able to conceal emotion; calma cool head
  5. lacking in enthusiasm, affection, cordiality, etca cool welcome
  6. calmly audacious or impudent
  7. informal (esp of numbers, sums of money, etc) without exaggeration; actuala cool ten thousand
  8. (of a colour) having violet, blue, or green predominating; cold
  9. (of jazz) characteristic of the late 1940s and early 1950s, economical and rhythmically relaxed
  10. informal sophisticated or elegant, esp in an unruffled way
  11. informal excellent; marvellous
  1. not standard in a cool manner; coolly
  1. coolnessthe cool of the evening
  2. slang calmness; composure (esp in the phrases keep or lose one's cool)
  3. slang unruffled elegance or sophistication
  1. (usually foll by down or off) to make or become cooler
  2. (usually foll by down or off) to lessen the intensity of (anger or excitement) or (of anger or excitement) to become less intense; calm down
  3. cool it (usually imperative) slang to calm down; take it easy
  4. cool one's heels to wait or be kept waiting
See also cool out
Derived Formscoolingly, adverbcoolingness, nouncoolish, adjectivecoolly, adverbcoolness, noun

Word Origin for cool

Old English cōl; related to Old Norse kōlna, Old High German kuoli; see cold, chill
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for cool

Old English col "not warm" (but usually not as severe as cold), also, of persons, "unperturbed, undemonstrative," from Proto-Germanic *koluz (cf. Middle Dutch coel, Dutch koel, Old High German kuoli, German kühl "cool," Old Norse kala "be cold"), from PIE root *gel- "cold, to freeze" (see cold (adj.)).

Applied since 1728 to large sums of money to give emphasis to amount. Meaning "calmly audacious" is from 1825. Slang use for "fashionable" is 1933, originally Black English; modern use as a general term of approval is from late 1940s, probably from bop talk and originally in reference to a style of jazz; said to have been popularized in jazz circles by tenor saxophonist Lester Young. Related: Coolly.


c.1400, "coldness, coolness," from cool (adj.). Meaning "one's self-control, composure" (the thing you either keep or lose) is from 1966.


Old English colian, "to lose warmth," also figuratively, "to lose ardor," from the root of cool (adj.). Meaning "to cause to lose warmth" is from late 14c. Related: Cooled; cooling.

Online Etymology Dictionary, © 2010 Douglas Harper

Idioms and Phrases with cool


In addition to the idioms beginning with cool

  • cool as a cucumber
  • cool down
  • cool it
  • cool off
  • cool one's heels
  • cool out

also see:

  • keep cool
  • keep one's cool
  • play it cool
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.