1. to do anything at all with
2. to do something with another person which might be considered, if not by you yourself, then by another person such as a girl/boyfriend, of an intimate nature
3. to mess around or joke around with
1. "yo, you fucking with your other boys tonight, or do you wanna shoot some hoops with me and jim?"
2. "yo, baby, trust me, im not fucking with any other girls, i promise you, when you saw me with marie, we were just walking cus i ran into her at a record store, thats all"
3. "you gotta be fucking with me, right, there is no way you went to england for 200 dollars roundtrip"
second person general possessional pronoun; origin probably from following analogy: my is to mine, as your is to yourn
"my shits is mine, your shits is yourn" - lil wayne