Harvard twist on the phrase fucks with which means to kick it with, hang out with, or chill with. Can also be used in an affirmatory response to a question.
From major hit motion picture "How High"
after Harvard is described to them
Silas: Shit, I'll fucks witcha!
Jamal: Shit, I'll fucks witcha, too!
Huntley: And that's a good thing?
Jamal: Yes. That's a "yes"!
Huntley: Then we'll "fox with" with each other.