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1.
A person who is known for being wrong about everything that is worth having an opinion about.

If you have a plan you want to follow you should ask their opinion about the plan. If they hate it, then you should probably go ahead and implement the plan. If they love it, then you need to go back to the drawing board as your plan will have deficiencies that you haven't been able to see, but the Known Idiot will have detected and loved.
Programmer 1: John is our known idiot, can you ask him what he thinks of your software design before implementing it?
Programmer 2: I asked him already - he thought it was a great idea....so I'll throw that design away and start again, it's obviously full of bugs.
by Danack August 12, 2013