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3.
"Ah-Duh" is a combination of the "Ah-Hah" moment of realization and the "Duh!" moment of having realized something that should have already been obvious. Ah-Duh therefore captures the feeling one has when one excitedly realizes the obvious and/or believes they've had sudden insight but then realizes they have "re-realized" something they already knew to be the case.
Wow, I just realized I can plug my iPhone into my axillary audio jack in my car and enjoy only the audio of online lectures and debates on Youtube. I normally think of Youtube has being only valuable for video! Ah-Duh!
by Matthew from Staunton November 05, 2010
 
1.
Ah duh is an expression used when something bad/annoying happens to yourself or a person near to you but it can be viewed in a funny light.

Derived from "ah damn", ah duh was thought to be a more lighthearted expression.

Pronounced "ah duurh", usually used in a combination with a hand gesture of the palm facing up with fingers locked into a "semi-claw" position.
"My girlfriend just dumped me"

Person 2 *hand gesture* + "Ah duh"

Alternatively once the word is understood, the hand gesture may be used in a singular form.
by Gead November 23, 2010
 
2.
THE BEST WORD EVER
It can be used it everyday conversation like you wouldn't belive
You can use it when you as another word for dumb, to just yell it in the halls, to make people laugh, just for the hell of it,to make fun of some,define a noun,it can honestly mean anything etc
Well arn't you a little AHDUH
The weather is a little on the ahduh side bro
AHDUH
Dude lets try and not be a ahduh today
My friends are a bunch of AHDUH
by Lildownz94 June 22, 2011