(Origin: This word was first used to my knowledge seven years ago when a friend of mine renamed an enemy in a video game from Dorp to Derp because it sounded funny.)
1: A stupid or incompetent person who believes that they are intelligent.
(I.E. President Bush)
2: A pathetic or unworthy adversary or opponent.
1: An intentionally stupid joke or action used to create a self-parody.
2: An easily aviodable mistake or flaw that is not addressed until it is too late to alter or fix.
<i>1: Man, our President is such a derp.
2: Those derps never stood a chance against me.</i>
<i>1: That joke was such a derp.
2: I really did not see the derp in my plan until it was too late.</i>