what's with

What's (up) with (someone)?

Why is someone so upset or acting in such an unusual way? What's with Jeff? He just screamed at me and stormed out of the room. I wonder what's up with Sarah—she's been avoiding me for days now.

what's with

Also, what's up with; what gives with. What is going on with; tell me about or explain it. For example, What's with all the food they're giving away? or What's up with Lee these days? or What gives with Jack? Why is he so glum? This idiom is also sometimes used as a substitute for how are you or what's wrong, as in Hi, Pam, what's with you? or What gives with you-why are you yelling? [Colloquial; c. 1940]