A person that screws up, every and anything good. They commonly annoy everyone around them, by claiming someone is wrong; even though they don't know anything to do with the subject. These are the people who do things like cut people off on the road, and take the last of something even though they don't want it. Usually no one likes this person.
"That guy over by the wall is being such a conter, he said my dad wasn't a lawyer."
"What a conter, I can't believe he was even invited here"