An archaic term meaning to impair or diminish the quality or value of something.
From Old French 'empeirier' (to make worse), derived from Latin 'peior' (worse), with the prefix 'a-' (to) creating the sense of making something worse.
This obsolete verb shows English once had different words for every shade of harm—'appair' specifically meant to make things worse, while we'd just say 'damage' today.
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