Someone who is operating in society and appears, by all means, to be "normal" and fully functional in their mental capacities. This person is not diagnosed as mentally challenged or retarded in any way, and yet they find ways to do things that are so stupid and moronic that they end up hurting themselves, ruining their careers and/or getting themselves posted on the news, YouTube and other social medias. The act is so bad, that it is disrespectful to those people in this world that actually do have mental retardation and/or are mentally challenged.
Did you hear about Plaxico Buress, the NFL player? He shot HIMSELF in the leg at a nightclub and now he's going to prison for 2 years. Man, that guy is a realtard.
That Tiger guy is a Realtard, he was the greatest golfer in the world and was on pace to break the record for Majors, but he could not keep it in his pants. When his wife found out, she chased him down the street with his own clubs and beat the shit out of his car until he crashed into a tree. That's about as Realtarded as it gets...