expression, noun
three-way playoff for the tournament championship
Sumo term: a playoff match involving three wrestlers who finished the tournament with the same record. The winner is determined by a round-robin format.
千秋楽に三つ巴の戦いが行われた。
A three-way playoff for the championship was held on the final day.
巴戦 is a more general term for a three-way playoff in sumo, while 三つ巴の戦い explicitly mentions 'three' and is a longer, more descriptive phrase.
From 三つ巴 (mitsudomoe, a three-comma symbol) + の + 戦い (tatakai, battle). The mitsudomoe symbol represents three entities in a circular, balanced struggle, which is metaphorically applied to a three-way playoff.