The Vocalibrate dictionary

arbiter

US/ˈɑrbɪtɚ/GB/ˈɑːbɪtə/noun

a person or group with the power to judge or settle disputes

The Supreme Court is the final arbiter of the Constitution.

Near in meaning: judgerefereeumpireauthority
In the family: arbitratearbitrationarbitrator

More words worth knowing

verisimilitudethe appearance of being true or real entropya gradual decline into disorder cabala small secret group plotting to gain power vicissitudean unexpected change in circumstances, often for the worse coteriea small, close group of people with shared interests pathosa quality that makes people feel pity or sadness