Able to be defended or protected; capable of being justified or protected against criticism or attack.
From defend (verb) + -able (suffix meaning 'capable of'). 'Defend' comes from Latin 'defendere' (de- 'away' + fendere 'to strike'). American English spelling variant of 'defenceable.'
A position in chess is 'defendable' even if it looks bad—you just need one solid argument to protect it, which is why the word appears constantly in legal and strategic writing.
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