noun.
In the Anglo-Saxon period of English history, a title meaning at first simply chieftain or lord, but later used specifically to denote the chief magistrate of a county or group of counties.
noun.
Hence In modern usage, a magistrate of a city or borough, next in rank to the mayor.
noun.
In England, a half-crown: a meaning explained by Brewer as containing an allusion to the fact that an alderman is a sort of half-king.
noun.
A turkey.