The quality of having strong or distinctive flavor.
From 'flavorous' plus '-ness', following the same pattern as flavorlessness. The '-ous' ending is preserved when adding '-ness' to create the abstract noun form.
This word is so rarely used that most dictionaries don't even list it—it's a great example of how English lets you create new words following grammatical rules, but that doesn't mean anyone actually speaks that way!
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