Sup is something cool people say. It can be used as a greeting. People say "sup" when they don't feel like saying whats up because it's to long. Also, people say "sup" because they get in the habit of saying "sup" so they just always say it. It can be used by girl or boy.

A euphemism for “kill me” now that composting oneself after one’s death has become popular.

A term that cool people use because they are too damn lazy to say What's up. (Too much effort involved there man.)

short for "what's up"

The correctly spelled contraction for what's up.

A contraction of the phrase "what's up?"

A different way of saying "whats up?"