noun
massive brawl; large-scale fight; melee
Refers to a chaotic, large-scale physical fight involving many people, often in public or in a competitive setting.
試合中に大乱闘が起きた。
A massive brawl broke out during the match.
昨夜のパーティーは大乱闘で終わった。
Last night's party ended in a huge fight.
喧嘩 is a quarrel or fight, often between individuals, whereas 大乱闘 implies a chaotic multi-person brawl.
Compound of 大 (large) and 乱闘 (brawl, melee). The exact historical derivation is uncertain, but the word is transparently formed from its components.