(chieflyUS,colloquial,sarcastic)An expression or exclamation that something is exceedingly obvious or apparent, or that one would have to be extremely foolish not to realize something immediately.[From 1962.]
It says here not to drive with the sun shade covering the windshield of your car. No duh!
A long pause was followed by Hannah saying, “Well, no duh!”
“What?”
“That sign. Did you read that sign?”
“No, what did it say?”
“It said ‘State Prison Next Exit: Do Not Pick Up Hitchhikers.’ That′s why I said, no duh! Like they have to tell people not to pick up hitchhikers.”
“That was a strange sign,” I agreed.
2008, Donald James Parker, All the Stillness of the Wind, page 127,
“I could maybe buy that one, for some who has advanced up the scale of faith. However, I have trouble believing it would be sellable to the general population.”
“That′s a big ‘no duh.’ Now, I hope you don′t mind me keeping your feet to the fire. Let′s get back to your idea that maybe there are multiple paths to Heaven. And by the way, I hope you know you′re making me dizzy.”
2010, Joselin Linder, Elena Donovan Mauer, Have Sex Like You Just Met - No Matter How Long You've Been Together, page xvii,
Ultimately, humans aren′t wholly monogamoue either. (Can we hear a “No duh,” from the bleacher seats?)
↑ no duh!, entry in 2008, Eric Partridge, Tom Dalzell, Terry Victor, The Concise New Partridge Dictionary of Slang and Unconventional English, page 460.