The eastsider is when you make the east coast gang sign, and apply it (to a girl) the same way as you would the shocker. This is done with the index and middle fingers together, and curled with the thumb, making a "c", while in the background, the ring and pinky are together, making the center line for the "e", thus representing east coast. The fingers would be applied to the clit, in the vagina and in the anus in a similar fashion to the shocker. Nothing says pimp, or gangsta more than fingering your girl with a gang symbol.
Yo holmes, what happened with that trick you hooked up wit?
Dude, gave her the eastsider, and she got freaky.
So did you hit it after that?