(Greek: ex, out; archo, rule)
Title used for both civil and ecclesiastical rulers.
In the civil administration of the Roman Empire, the exarch was the governor of any important province, as the Exarch of Italy at Ravenna (552-751).
In ecclesiastical language an exarch was at first a metropolitan with jurisdiction beyond his own province.
The term came gradually to be restricted to the metropolitans of Ephesus, Caesarea, and Heraclea.
In the West the title of exarch has disappeared, being replaced by "vicar Apostolic" and "primate."
In the East the title is given to a bishop who holds a place between that of patriarch and of ordinary metropolitan.
The most famous of those bearing the title now is the Bulgarian exarch at Constantinople.
New Catholic Dictionary