Defintion: A person who behaves like an asshole; a person that is inconsiderate or inpolite.
History: Though it takes it's name from a person being especially tool-like at a concert and pushing people aside when there was no path or movement simply because they are bigger, the phrase is expanded to serve to describe any kind of person who behaves like an asshole in any situation. It does not attempt to make any loathing against those who wear sweatervests in normal life situations, but it is notably strange to wear one into the GA section of a punk-rock concert.
"Yeah, what a sweatervest!"
Girl 2: God, he's so hot. I wish more boys had style like him.
Girl 3: No way, because then that guy wouldn't be special and unique and sexy!
Girl 4: But how are we all going to have him?
Girl 5: I'm not sharing with you bitches.
That report on the War in Afghanistan was definitely sweatervested to hide the truth.
The catholic church is constantly sweatervesting the past.
That news report was such a sweatervest.