Similar to MILF, MILK stands for Mother I'd Like to Kill.
Guy 1: "How was your date with Angie? Did you get to meet her parents?"
Guy 2: "Oh Angie's great but her mom is such a MILK! Wouldn't shut up about how I was ten minutes late and how 'irresponsible' I am."
A plum is also a person who is a symbol of peace. There are the Bloods, who are red, and the Crips, who are blue, and then there are the Plums, who are purple (a combination of the two, if you will).
Plums are also ultra fly people who spend their time being stared at for their pure beauty and awesomeness. They rarely say stupid things and are farther away from the previous (idiotic) definition of "a short fat kid" than the Earth is from the sun.
: I'ma kill you!!
: No, i'ma kill you!
: Come on guys...
: You know, I thought I was cool, but that was before I met a plum.
: DAMN! You are so lucky...I wish I was a plum.