(law) the hearing and determination of a dispute by an impartial referee agreed to by both parties (often used to settle disputes between labor and management) WordNet 3.0 & Open English WordNet

Arbitration is a form of alternative dispute resolution that resolves disputes outside the judiciary courts. Wikipedia

Technique for the resolution of disputes Wikidata

A process through which two or more parties designate a third party whose ruling they will accept formally. OmegaWiki

In general, a form of justice where both parties designate a person whose ruling they will accept formally. More specifically in Market Anarchist (market anarchy) theory, arbitration designates the process by which two agencies pre-negotiate a set of common rules in anticipation of cases where a customer from each agency is involved in a dispute. Wiktionary

Form of justice. Wiktionary (translation)