adjective, cool·er, cool·est.
1.  Moderately cold; neither warm nor cold: a rather cool evening.
2.  Feeling comfortably or moderately cold: I’m perfectly cool, but open the window if you feel hot.
3.  Imparting a sensation of moderate coldness or comfortable freedom from heat: a cool breeze.
4.  Permitting such a sensation: a cool dress.
5.  Not excited; calm; composed; under control: to remain cool in the face of disaster.