203 Free-for-all
(PW) mayhem, disorder
When the teacher left for a meeting, it was a free-for-all in the classroom.
(MW) Function: noun Date: 1881
a competition, dispute, or fight open to all comers and usually with no rules : brawl; also : a chaotic situation resembling a free-for-all especially in lacking rules or structure
— free–for–all adjective
(free) n.
A disorderly fight, argument, or competition in which everyone present participates. See Synonyms at brawl.
Informal a disorganized brawl or argument, usually involving all those present
(phraseFinder)
Originally, a "race or competition" (Webster's 2nd, unabridged) that anyone is free to enter. Later, a fight that everyone joins in.