1. 仲裁人;公断人
An arbiter is a person or institution that judges and settles a quarrel between two other people or groups.

2. （时尚或风格的）权威，决定者
An arbiter of taste or style is someone who has a lot of influence in deciding what is fashionable or socially desirable.

1. someone chosen to judge and decide a disputed issue

e.g. the critic was considered to be an arbiter of modern literature
the arbitrator's authority derived from the consent of the disputants
an umpire was appointed to settle the tax case

Synonym: arbitratorumpire

2. someone with the power to settle matters at will

e.g. she was the final arbiter on all matters of fashion

Synonym: supreme authority