1. what is happening; what is going on:
- You can keep up to date on what’s happening with legislation, new product research, or what’s up in your community.
2. (U.S. sl., also: whassup) is used as a greeting to someone you know well:
- “Hi, Jim. What’s up?” “Oh nothing much…. How are you doing?”
what’s up with—what’s wrong with:
- Four out of ten days I have had to weather tornado and flash flood warnings. What’s up with the weather?