This act is mostly performed by potheads and slightly autistic- or socially inert people.
Look at that girl, she's totally gerritting the other guy. I guess she didn't like it that he couldn't hold his bart..
person 1: What did Kay say about it?
person 2: I dont know, I was unable to finish my story 'cause Florian totally gerritted me with his fat body and started telling Bart about his poop in the fridge..
person 1: Lame...