What is a duel between three people called?
A duel involving three opponents is a truel. Those involved in a truel can fire at each other with the goal of eliminating the others while personally surviving. Truels are frequently studied as part of game theory. This is a niche in mathematics that studies models of strategic interaction that are possible and/or probable among rational decision-makers. It's usually assumed that each player involved in the truel wants to be the last man standing. It's also assumed that each player will behave in a logical manner that maximizes the probability of survival. Source: MindYourDecisions.com