arbiter

Noun

• someone chosen to judge and decide a disputed issue
  • 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
    

• someone with the power to settle matters at will
  • she was the final arbiter on all matters of fashion
    

Related words

• Synonyms: 
  arbitrator , umpire , supreme authority