1. An action or pattern of actions consistant with those of a knucklehead, or a person with questionable intellegence.
2. Minor actions of innapropriate, silly, or inconsiderate behavior or behavior that causes a mild nuisance, not necessarily with such intent by the actor. It is not as severe as douchebaggery.
Shawn: Man I wish those people over there would keep it down. They are starting to bother me.
Dave: Yes, there is quite a bit of knuckleheadery going on over there.
Teacher: Hey, cut out the knuckleheadery and get your work done!