One who deans or serves as a dean; someone acting in the capacity of a dean.
From dean + -er (one who does). This agent noun is theoretically possible but rarely used in practice, as 'dean' itself already serves as a noun for the person holding the position.
A 'deaner' would theoretically be someone acting as dean, but in practice nobody uses this word—you'd just say 'the dean' instead, showing how English doesn't need to create agent nouns for every occupation.
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