The word you say to great your gangsta buddies. The gang version means lets meet up and bang someone. The version you say to someone else means I want to bang you.
A phrase extremely overused by people who are getting shittttyy! Often used as a retorical question agreeing to another persons comment instead of actually asking someone whats up.
When you and someone else are in an argument, and the other person says they are better than you (scored more goals in a game, got a better grade, etc.) and you tell them you got the better grade or what not, adding on the end, "sup dude?" in a nonchalant manner, just to rub it in.
Jake- "Hey man, how'd you do on the test last week?"
Mike- "I got a 95, how'd you do?"
Jake- "I got a 98, sup dude?"