Webster's Revised Unabridged Dictionary · 1913

Cool

Cool , adjective

[Anglo-Saxon cōl; akin to Dutch koel, German kuhl, Old High German chouli, Danish kolig, Swedish kylig, also to Anglo-Saxon calan to be cold, Icelandic kala. See Cold, and compare Chill.]

1.
Moderately cold; between warm and cold; lacking in warmth; producing or promoting coolness.
Fanned with cool winds. — Milton
2.
Not ardent, warm, fond, or passionate; not hasty; deliberate; exercising self-control; self-possessed; dispassionate; indifferent; as, a cool lover; a cool debater.
For a patriot, too cool. — Goldsmith
3.
Not retaining heat; light; as, a cool dress.
4.
Manifesting coldness or dislike; chilling; apathetic; as, a cool manner.
5.
Quietly impudent; negligent of propriety in matters of minor importance, either ignorantly or willfully; presuming and selfish; audacious; as, cool behavior.
Its cool stare of familiarity was intolerable. — Hawthorne
6.
Applied facetiously, in a vague sense, to a sum of money, commonly as if to give emphasis to the largeness of the amount.
He had lost a cool hundred. — Fielding
Leaving a cool thousand to Mr. Matthew Pocket. — Dickens

Cool , noun

A moderate state of cold; coolness; -- said of the temperature of the air between hot and cold; as, the cool of the day; the cool of the morning or evening.

Cool , transitive verb

1.
To make cool or cold; to reduce the temperature of; as, ice cools water.
Send Lazarus, that he may dip the tip of his finger in water, and cool my tongue. — Luke xvi. 24
2.
To moderate the heat or excitement of; to allay, as passion of any kind; to calm; to moderate.
We have reason to cool our raging motions, our carnal stings, our unbitted lusts. — Shakespeare
Collocations (1)
To cool the heels , to dance attendance; to wait, as for admission to a patron's house. [Colloquial] — Dryden

Cool , intransitive verb

1.
To become less hot; to lose heat.
I saw a smith stand with his hammer, thus, the whilst his iron did on the anvil cool. — Shakespeare
2.
To lose the heat of excitement or passion; to become more moderate.
I will not give myself liberty to think, lest I should cool. — Congreve