get with (someone or something)
1. To be knowledgeable about and engaged with something. The boss is gong to want us to know exact figures in the meeting, so you better get with it.
2. slang To have a romantic or flirtatious interaction with someone. A: "Did you get with that girl?" B: "Yeah, we kissed a few dates."
3. slang To have sex with someone. I wouldn't be surprised if he got with her last night after the party—they were very flirty all night.
get with something
to become alert. (Often with it.) Hey, stupid. Get with it! Wake up, Bill. Get with what's going on!
To become involved with or attuned to some activity; be properly engaged with something: You need to get with the project and start helping us.