Source : Webster's Revised Unabridged Dictionary (1913)

Arbiter \Ar"bi*ter\, v. t.
   To act as arbiter between. [Obs.]

Arbiter \Ar"bi*ter\, n. [L. arbiter; ar- (for ad) + the root of
   betere to go; hence properly, one who comes up to look on.]
   1. A person appointed, or chosen, by parties to determine a
      controversy between them.

   Note: In modern usage, arbitrator is the technical word.

   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.

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

Source : WordNet®

arbiter
     n 1: someone with the power to settle matters at will; "she was
          the final arbiter on all matters of fashion" [syn: {supreme
          authority}]
     2: someone chosen to judge and decide a disputed issue [syn: {arbitrator}]