hook up with (someone)
1. slang To meet with or join someone. I'm running late, so I'll just hook up with you guys there.
2. slang To work together with someone. Yeah, but if you hooked up with Joe, you guys could pool your resources and really get some stuff done in this town.
3. slang To have a casual sexual encounter with someone. I can't believe you hooked up with my ex-boyfriend!
hook up with someone
1. Fig. Inf. to meet with someone. Fancy hooking up with you here, Bill. How have you been? Well, hello, Tom. I didn't think I'd hook up with you again so soon.
2. Fig. to join forces with someone. If we hook up with each other it'll be easier to defeat the others. These two competitors have hooked up together and we now have a real problem.