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1.
whoever the person is below me is wrong.
all up in my grill doesn't necessarily mean in someone's business.

it means someones in your face.
grill = face.

therefore, it can also be used describing someone who is excessively annoying and bothering you.
That ho was all up in my grill. Tell him to get his nasty, annoying self outta my face.
by mahal April 20, 2005
 
2.
all up in my grill means when someone is all up in your business or all up in your body area
guy comes up places hand on girls boob
girl says: oh boy...you are all up in my grill, you better get off
by Stephanie April 26, 2004