n. The ruler of a province in the Byzantine empire. The most important was the exarch of Ravenna. See exarchate.n. In the early church, a prelate presiding over a diocese: as, the exarch of Ephesus. The title is often used as synonymous with patriarch; but strictly the exarch was inferior in rank and power to the patriarch, and superior to the metropolitan.n. In the Gr. Ch., a legate of a patriarch, whose duty it is to sustain the authority of the patriarch, and to obtain accurate information concerning the lives of the clergy, ecclesiastical observances, monastic discipline, etc., in the provinces assigned to him. The power of the exarchs is very great. They can absolve, depose, or excommunicate in the name of the patriarch.