A foolish and fairly stupid person, usually online, who is generally completely oblivious to how much of an idiot they come off as. They usually have poor grammar, bad social skills and there's seldom anything thought provoking or even remotely
interesting about their opinions and/or they post things that are ridiculously off topic to the discussion at hand.
There are two flavors of them: the young and immature garden variety Dunks and then the trollish, masochistic lifelong ones with something seriously wrong with them
emotionally and mentally. Most Dunkasses are often young and usually mellow out as they get older and learn better netiquette, some even becoming valued and productive members of the community in question, though a rare few, people like
Christian Weston Chandler, will stay completely unrepentant, stubbornly refusing to learn from their mistakes and learn social skills. A lifelong Dunkass often ends up with a long list of communities from which they've been banned and a bad reputation across their fandom or community.