Green’s Dictionary of Slang

cool adj.

[ult. orig. Eton College jargon cool fish, a cocky, self-possessed schoolboy, itself rooted in the older SE meaning: dispassionate, cold-blooded, later self-contained, calm; post-WWII use (initially US black) is usu. associated with the cool jazz movement of the 1940s, esp. Charlie Parker’s record Cool Blues of 1947, but the available cits. show older usage in a number of senses, and as with a number of slang’s (rare) abstract terms, it is less than simple to draw hard-and-fast lines between the senses, whether sl., colloquial or SE]

1. [mid-19C+] relaxed, calm, self-contained; often as imper., e.g. be cool!

2. [19C+] insolent, arrogant, impudent.

3. [late 19C+] (orig. US) of people, sophisticated, aware.

4. [late 19C+] good, fine, pleasing, admirable, a general positive sense.

5. [late 19C+] (orig. US) of a person, place or object, fashionable, stylish, chic, ‘with it’.

6. [1940s+] antonyms of hot adj.

(a) (drugs) not carrying or owning drugs, or believing that one has hidden them well enough to defy any search of one’s body or premises.

(b) (US Und.) not suspicious, either of people or objects.

(c) (US street gang) not carrying weapons or acting aggressively.

7. [1950s+] acceptable, satisfactory; esp. in phr. (that’s) cool, fine, ok.

8. [1960s+] comfortable, happy, on good terms.

9. [1970s] safe.

10. [1970s+] trustworthy.

In derivatives

coolster (n.)

[1950s] (US teen) a gang member, a 'hip' teenager; also attrib.

In compounds

cool-brains (adj.)

[1960s+] (S.Afr.) relaxed, in control.

cool breeze

see separate entries.

cool cat (n.)

[1940s+] a sophisticated, competent, unruffled, able person; also attrib.

cool hand (n.)

1. [mid-19C+] a cool, calm, controlled and competent individual.

2. [20C+] (US) a cool, unruffled demeanour.

cool-head (n.) [note SE cool-headed]

1. [1960s+] a pleasant person.

2. [20C+] a calm, unflappable person.

cool jerk (n.)

[1960s–80s] (US black/teen) one who deludes himself into a belief that he is sense 3; in fact he is a jerk n.1 (3); thus do the cool jerk, to move in an ostentatious manner.

cool papa (n.)

[1940s] (US black) a self-possessed, sophisticated and, as such, alluring man.

cool whip (n.) [pun on brandname of the US sweet]

[1980s+] (US campus) something very new and appealing.

In phrases

be cool (also you be cool)

[1980s+] goodbye.

cool as shit (also cool as toast)

[1970s+] (US campus) an expression of approval.

cool by the pool

[2000s+] (S.Afr.) a positive response to a question such as ‘how’s it going?’.

cool like a moose (adj.)

[1960s] (US teen) all wrong, whether socially, regarding fashion, work, amusements, etc.

cool runnings

[1980s+] (W.I./UK black teen) a phr. meaning everything is fine, all is going smoothly.

on the cool

[2000s] (US prison) a general intensifier, usu. meaning truthfully or its opposite.

that’s cool

[1950s+] (orig. US) that’s satisfactory, that’s all right, don’t worry.

too cool for school (adj.)

[1990s+] very fashionable, well-dressed, obsessively so.

In exclamations

cool beans!

[1980s+] (US teen) excellent! wonderful!

cool deal! [deal n.1 (4)]

[1990s+] (US campus) an exclamation of approval, admiration.

SE in slang uses

In compounds

cool crape (n.) [‘Cool-crape, a slight Chequer’d Stuff made in imitation of Scotch Plad’ (B.E.)]

[late 18C] a shroud; thus be put into one’s cool crape, to die.

cool lady (n.) [cool nantz ]

[late 17C–early 19C] a female camp follower, specializing in selling brandy to the troops.

cool nantz (n.) (also cool nant(e)s) [nantz n.]

[late 17C–early 19C] cognac.

cool one (n.)

[1950s+] (orig. US) a bottle of beer.

cool smoke (n.)

[1980s+] (drugs) a smoke of methamphetamine.