Arbiter

Part of speech: noun (n.)

1. A person appointed, or chosen, by parties to determine a controversy between them.

2. Any person who has the power of judging and determining, or ordaining, without control; one whose power of deciding and governing is not limited. For Jove is arbiter of both to man. Cowper.

Synonyms: Arbitrator; umpire; director; referee; controller; ruler; governor.

Part of speech: verb (v.)

To act as arbiter between. [Obs.]