arbitrator (n.)
"person chosen by opposite parties to decide some point at issue between them," early 15c., from Late Latin arbitrator "a spectator, hearer, witness; a judge," agent noun from past participle stem of arbitrari "be of an opinion, give a decision," from arbiter "a judge, umpire, mediator" (see arbiter).
The legal form of popular arbiter. In modern usage, an arbiter makes decisions of his own accord and is accountable to no one but himself; an arbitrator decides issues referred to him by the parties. "It is often the practice to appoint two or more arbitrators, with an umpire, chosen usually by them, as final referee" [OED].
Dictionary entries near arbitrator
arbitrage
arbitral
arbitrary
arbitrate
arbitration
arbitrator
arbitrer
arbor
Arbor Day
arbor vitae
arboreal