A "Wiki Wonder" is someone who posts on forums or blogs to let everyone know how smart they think they are. They want you to believe they know what they're talking or they have the definitive answer to a topic because they looked it up on wiki. In reality all they know is how to spell "wiki".
Or worse yet, they spew their answer without telling you they looked it up on wiki, as if they are somehow highly intelligent.
Dude I know what I'm talking about...I looked it up on wiki.
That ass hat don't know shit. He's nothing but a Wiki Wonder.