A person or a thing who is dumb and or a maniac, or just a nickname for your friend when they are acting crazy.
Hannah:Stop acting like such a freaking fuddernudder!
Andrew: I'm sorry, I will stop acting like a fuddernudder!maniac
Andrew: I'm sorry, I will stop acting like a fuddernudder!maniac
by 21:D June 09, 2010