Acceptable or adequate enough to be approved or allowed, though not necessarily excellent or outstanding.
From Old French 'passable,' derived from 'passer' (to pass). The suffix '-able' means 'capable of being,' so passable literally means 'capable of being passed' or 'allowed to pass.'
Passable is the vocabulary of the mediocre—it's what teachers write on reports when they're being polite about work that's merely 'okay,' making it perhaps the most diplomatic word for 'not great.'
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