hierarch

1. One who occupies a position of authority in a religious hierarchy.
2. One who occupies a high position in a hierarchy: governmental hierarchs.

[From Middle English jerarchis, hierarchs, from Medieval Latin hierarcha, dignitary, prelate, from Greek hierarkhēs, high priest : hieros, holy + -arkhēs, -arch.]

noun

One who is highest in rank or authority: boss, chief, chieftain, director, head, headman, leader, master. Slang honcho. Idioms: cock of the walk. See over/under.

The noun has one meaning:

Meaning #1: a senior clergyman
  Synonyms: archpriest, high priest, prelate, primate