Source : Webster's Revised Unabridged Dictionary (1913)

Eparch \Ep"arch\, n. [Gr. ?; over + ? chief, ? supreme power,
   dominion.]
   In ancient Greece, the governor or perfect of a province; in
   modern Greece, the ruler of an eparchy.

Source : WordNet®

eparch
     n 1: a bishop or metropolitan in charge of an eparchy in the
          Eastern Church
     2: the governor or prefect of an eparchy in ancient Greece