1. Someone who studies and settles conflicts and disputes: An adjudicator, or umpire, was needed in the racing competition in order to make sure that all of the rules were abided by and that no team could have an advantage over the others.
2. A person who presides, judges, and arbitrates during a formal dispute: The term adjudicator essentially means a judge, without invoking that legal term.

Because the two girls were thought to have stolen cigarettes and cosmetics in the store, which they denied, an adjudicator had to deal with this offense and determine the truth.