Someone that is always trying to one-up you with his latest gleanings from wikipedia. Unfortunately, he is usually wrong, butting into the conversation, or giving unrelated or unwarranted information.
During a conversation between person A and person B, person C will jump in with, "Oh you didn't know that? According to wikipedia..."
Person A responds, "We did know that, but we weren't really talking about that, anyway. Thanks Wiki-dumbass!"