Someone who does themselves no favours what so ever. They do not care how they affect other people and just try to fuck up everybodys way of living. Someone who performs a ruthless and inconsiderate act thus making them a cunt.
John: I can't believe the ref sent Rooney off, Dave!
Dave: Yeah I know John! He was being a Grade A cunt! Wasn't he John?
John: Yes he was Dave!