What is All Up In It?
1.
to be nosy; to annoyingly look at or comment about someone's food(how the food looks, smells... etc.); to ask who ask someone who they are on the phone with; to look over someone's shoulder when they are reading(books, magazines, computer screen... etc), to ask, comment, or pry into someone's personal life.
This phrase simply means that someone is bugging you about what is going on with you. The phrase is a playful way to tell someone to back off of you and to get out of your business.
This phrase is especially useful in the workplace where many people are in close quarters.
Example 1:
ADAM:(from the next cubicle): Wow... that smells good. What is that? Where did you get that from? Can I have a bite?
MARY: Dude, why are you all up in it?
Example 2:
MARY: Hey, was that really Sally that you just got off of the phone with? Are you still going out with her?
ADAM: Damn! All up in it!
See