single combat 
noun [mass noun]
Fighting between two people: he defeated the enemy champion in single combat...
- The parties, or champions on their behalf, would fight in formal single combat and the winner would be deemed to be the successful party in the case.
- The tournament in this period was no carefully regulated single combat, but a great mêlée involving hundreds of knights, mimicking and rehearsing for warfare.
- Although gladiators were clearly Roman, the values presented in gladiatorial single combat were central to Greek culture as well as to Roman.