Johno wrote:
dictionary's decribe cool as

Neither warm nor very cold; moderately cold: fresh, cool water; a cool autumn evening.

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
.
Of, relating to, or characteristic of colors, such as blue and green, that produce the impression of coolness.
Slang.
Excellent; first-rate: has a cool sports car; had a cool time at the party.

Acceptable; satisfactory: It's cool if you don't want to talk about it.
Slang. Entire; full: worth a cool million.

adv.
Informal. In a casual manner; nonchalantly: play it cool.