Yes, cool is playable
...and is worth 8 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Cool" Definition
noun
A cool place, part, or time: the cool of early morning.
Composure; poise: "Our release marked a victory. The nation had kept its cool” ( Moorhead Kennedy).
The state or quality of being cool.
A cool time, place, or situation.
Absence of excitement or emotional involvement.
idiom
Cool it Slang To calm down; relax.
Cool it Slang To stop doing something.
adjective
Giving or suggesting relief from heat: a cool breeze; a cool blouse.
Marked by calm self-control: a cool negotiator.
Marked by indifference, disdain, or dislike; unfriendly or unresponsive: a cool greeting; was cool to the idea of higher taxes.
Neither warm nor very cold; moderately cold: fresh, cool water; a cool autumn evening.
Of, relating to, or characteristic of colors, such as blue and green, that produce the impression of coolness.
adverb
Informal In a casual manner; nonchalantly: play it cool.
In a casual and nonchalant manner.
verb-transitive
Physics To reduce the molecular or kinetic energy of (an object).
To make less ardent, intense, or zealous: problems that soon cooled my enthusiasm for the project.
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