Definition of cool
1
: moderately cold : lacking in warmth
- The plant grows best in cool climates.
2 a
: marked by steady dispassionate calmness and self-control
- a cool and calculating businessperson
b
: lacking ardor or friendliness
- a cool impersonal manner
d
: free from tensions or violence
- We used to fight, but we're cool now.
3
—used as an intensive
- a cool million dollars
4
: marked by deliberate effrontery or lack of due respect or discretion
- a cool reply
5
: facilitating or suggesting relief from heat
- a cool dress
6 a
of a color
: producing an impression of being cool;
specifically
: of a hue in the range violet through blue to green
7
slang
b
: fashionable, hip
- … not happy with the new shoes … because they were not "cool."
- —Celestine Sibley
