Definition:

: foolish, empty, and often specious talk, writing, ideas, or opinions

Example:

"On the credibility spectrum, these theories fall somewhere between pseudoscience and straight-up flapdoodle." – Chris Gay, U.S. News & World Report, December 5, 2012

About the Word:

If anyone insists they know the origin of flapdoodle, their explanation is probably flapdoodle. We don't know where the word came from, but it probably began as an alteration of some other absurd word – the obsolete word fadoodle is one candidate.