someone who presides, judges and arbitrates during a formal dispute

An adjudicator is someone who decides on a winner at a competition for music or theatre. The adjudicator will always be somebody who has a lot of experience in what he is adjudicating. In big international festivals, a team of several adjudicators may decide together on the winners. In amateur competitions, the adjudicator may also talk to the competitors after they have performed and give them advice. Competitors are often given first, second and third prizes.

In Law, an adjudicator is someone who decides who is right when a group of people cannot agree on something.