adj.
    - of or at a fairly low temperature. 
▸(especially of clothing) keeping one from becoming too hot.
 - not excited, anxious, or emotional. 
▸unfriendly or unenthusiastic.
 ▸(of jazz) restrained and relaxed.
 - informal fashionably attractive or impressive. 
▸excellent.
 ▸used to express acceptance or agreement.
 - 
(a cool ——)
 informal used to emphasize the size of a sum of money:
 they pocketed a cool $1 million each.
 
n.
 
(
the cool)
 a cool temperature, place, or time.
v.
   - become or make less hot.
 - become less emotional or enthusiastic.
 - 
(cool out)
 informal relax:
 a dreamy spot where you could cool out and detox.
 
 
  Phrase
  
    
      - keep 
(or lose)
 one's cool
 informal maintain (or fail to maintain) a calm and controlled attitude. 
    
   
  Derivative
  
    - coolish adj.
  - coolly adv.
  - coolness n.
 
   
  Etymology
  OE cōl (n.), cōlian (v.), of Gmc origin; rel. to cold.