Nonsense, humbug, or pretentious talk that doesn't mean anything real.
A reduplicative compound (repeating words with slight changes) from 'flub' combined with an onomatopoetic 'dub.' Emerged in American English in the 19th century as informal slang.
Flubdub is pure onomatopoeia—it sounds like the blathering of someone talking complete nonsense. These reduplicative words like flubdub, hullabaloo, and gobbledygook were invented by writers to actually sound like their meanings.
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