One who exhibits qualities of incompetence, social maladjustment, fashion retardation or just general dumbassness that far exceed those possessed by a run-of-the-mill dork.

a huge dork
uber is German for over
Triumph the Insult Comic Dog came up with this terminology during his visit to the Star Wars Fan Convention outside Ziegfield Theater

uber = american take on german word meanig above ("extreme", "awesome", etc in 'american')
dork = idiot, unintelligent, dumb

work it out

a greeting of two friends.