Credit has been given to Homer Simpson for this word but I first heard it used back in Clifton High School in New Jersey back in 1968 by Ed S. and by a bunch of his school buddies with the added striking of the side of the head with the palm of the hand for emphasis. The meaning which has already been described by other posters is EXACTLY as it was back then. Sorry Homer...
doh: No examples needed, first examples are accurate, Ed S. gets the credit.
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