Twenty-seven years a cool cat, and now it has to be a crazy little midget that gets to you. Exile from Space Judith Merril. Slang definitions & phrases for cool cat. Cool. Neither warm nor very cold. Neither mean nor very nice. Cool is the person that is in between evey genre of people. It is the chain that binds the mean and. Definition of cool cat in the Idioms Dictionary. cool cat phrase. Finally, Farlex brings you all the rules of English grammar, all in one place, explained in simple.