So most likely the reason your searching this up is
1: Your a freaking idiot
2: Your parent/relative walk into the room and you just searched up Sup
3: Your pure bored
Sup is just cool way of saying hi.
Mark: Sup Angie wanna hang out
Angie: Get a life
Or
Sally: Whatâs up Stephanie!
Stephanie: Iâm moving to California...