Past tense of dean as a verb; to serve as or act in the capacity of a dean of a college or cathedral.
From dean (a senior administrative or clerical official) + -ed (past tense). While dean is primarily a noun, it can be verbed in formal academic or ecclesiastical contexts to mean 'served as dean.'
You rarely hear 'deaned' in conversation—it's such formal academic language that most professors would just say 'served as dean' instead, showing how some verbed nouns never quite catch on.
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