cool cat

noun2

1. •
   A person who performs or appreciates jazz, especially one whose style of speech and movement is relaxed and rhythmic.

   • Step up and take a look at the U.S.'s latest secret weapon. A hot missile? No, a cool cat—Earl ("Fatha") Hines, jazz pianist nonpareil. — 1966
2. •
   A person who is at ease and self-assured; one who is calm and composed in interactions with others.

   • "I've talked to a lot of young people, and they're all very excited that he's such a cool cat—not black or white or anything like that—just such a cool guy." — 2008