It means someone who is ABSOLUTELY dumb. Dumb person of the 1st order. Someone who is so dumb that they make a donkey look smart.
When someone has just done something absolutely stupid or said something absolutely dumb, you can say, "Hey tony, you are the most duh dumb person i have ever met."
by Gia Khanna June 22, 2009
Get the Duh Dumbmug.