The quality or state of being beefy; muscularity, strength, or the characteristic of being substantial and solid.
From 'beefy' + noun suffix '-ness'; 20th-century formation describing the abstract quality of beef-like characteristics.
Abstract nouns made from slang (like 'beefiness') sound funny to formal speakers, but they're how language systematically creates whole families of related words—every adjective can theoretically generate a '-ness' noun.
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