Infinitely and effortlessly cool. Root word: Julian Casablancas. Can be used as noun, verb, or adjective!
"Did you see that guy!?"
"Pfsh, guy was SUCH a Casablancas"
"What are you up to?"
"Oh nothing much, just Casablancasing it"
"How's the horchata?"
"Oh, seriously Casablancas, thank you"