What is All Up On?
Used to mean an encroachment of personal privacy or space, invited or uninvited. Some form of pressure, either physical or mental, i.e. a woman dancing really close to another guy; a landlord pressuring for rent.
Can be used to imply sexual interest, as in someone who is intensely flirting/
Girl was all up on him in the club, backin her booty up.
She was all up on him, wouldn't leave him alone, tryin to get his number n shit
Damn, why you all up on me? I'll get you your shit, I swear.
(def 1) On top of, either in a literal or metaphorical sense.
(def 2) Pursuing or showing interest in.
(def 3) Imminent or present.
Cultural note: This phrase has received some popularity due to it's occasional use by the character Strong Bad on the Homestar Runner website.
(def 1) George had three puppies, and every time he sat down to watch TV they were all up on his lap.
(def 2) Commercials would have us believe that a guy just has to use the right brand of deodorant and the ladies will be all up ons him.
(def 3) So it's finally Halloween and the Autumn months are all upon us.