often refers to a mentally unstable person known for his/her outbursts of petty and worth-loathing violence. Without much success in life such individuals will try to establish themselves as beautiful or stylish. They,however,resemble a horse in most cases and cause embarrassment as one doesn't know whether to feed them a carrot and stroke their mane or not.
Dude1: Wow! Look at that horse go mental.
Dude2: Yeah,he's pulling a tea kramer.