What does "what's up" mean?
Native speaker’s answer
Rebecca
"What's up" is a casual greeting that means "what are you doing?" or "what's going on?" We use this quite often around people we know well. It's almost like saying hi, but you want to know what they are currently doing. Ex: A: Hey, what's up? B: Not a whole lot. Just watching t.v. Ex: A: What's up? B: Playing video games.