ar·bi·ter 
(ärbĭ-tər)
(ärbĭ-tər)n.
1. One agreed upon or appointed to judge or decide a disputed issue; an arbitrator.
2. One whose opinion or judgment is considered authoritative or worthy of respect: an arbiter of fashion.
[Middle English arbitre, from Old French, from Latin arbiter, of Phoenician origin; see ʿrb in the Appendix of Semitic roots.]