The Collaborative International Dictionary of English v.0.48:

Antonomasia \An`to*no*ma"si*a\ (?; 277), n. [L., fr. Gr. ?, fr.
   ? to name instead; ? + ? to name, ? name.] (Rhet.)
   The use of some epithet or the name of some office, dignity,
   or the like, instead of the proper name of the person; as
   when his majesty is used for a king, or when, instead of
   Aristotle, we say, the philosopher; or, conversely, the use
   of a proper name instead of an appellative, as when a wise
   man is called a Solomon, or an eminent orator a Cicero.
   [1913 Webster]