noun
brawl outside the ring; ringside fight
Used in professional wrestling and combat sports for a fight that spills outside the ring or occurs outside the designated competition area.
試合中に場外乱闘が始まり、観客は大興奮だった。
A brawl outside the ring broke out during the match, and the crowd went wild.
noun
verbal fight via the media; media war of words
Idiomatic extension: a public dispute or heated exchange conducted through the media, as if fighting outside the ring.
政治家同士の場外乱闘が連日ニュースを賑わせている。
The media war of words between the politicians has been making headlines every day.
Compound of 場外 (outside the venue/ring) and 乱闘 (brawl, melee). The idiomatic sense extends the image of a physical fight to a public verbal dispute.