|1.||Dewey defeats Truman|
(Noun) A large blunder or mistake; an inaccuracy
Today our sociology professor said that dolphins are fish. What a Dewey defeats Truman-she should check her facts.
"Shit! After I printed out my essay, I realized I had made a few punctuation and spelling errors."
"Hey, don't worry. It's no Dewey defeats Truman"