Short for Super. Basically meaning really awesome or cool.
Also used as a shorter word for Superman. Mainly used by comic book writers.
Dude, how are you going to jump off that ladder? You're Supes High Up!
Bro, those shoes are totally supes!
Hey, Bill. Did you finish writing the comic strip for Supes yet?
Hey, Simon. You know that the new Supes Movie just cameout?