1: moderately cold : lacking in warmth
2
a: marked by steady dispassionate calmness and self-control (a cool and calculating administrator - Current Biography)
b: lacking ardor or friendliness (a cool impersonal manner)
c: of jazz : marked by restrained emotion and the frequent use of counterpoint
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
b: of a musical tone : relatively lacking in timbre or resonance
7
slang
a: very good : excellent; also : all right
b: fashionable, hip (not happy with the new shoes - because they were not cool - Celestine Sibley)
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cool, composed, collected, unruffled, imperturbable, nonchalant mean free from agitation or excitement. cool may imply calmness, deliberateness, or dispassionateness (kept a cool head). composed implies freedom from agitation as a result of self-discipline or a sedate disposition (the composed pianist gave a flawless concert). collected implies a concentration of mind that eliminates distractions especially in moments of crisis (the nurse stayed calm and collected). unruffled suggests apparent serenity and poise in the face of setbacks or in the midst of excitement (harried but unruffled). imperturbable implies coolness or assurance even under severe provocation (the speaker remained imperturbable despite the heckling). nonchalant stresses an easy coolness of manner or casualness that suggests indifference or unconcern (a nonchalant driver).