The Collaborative International Dictionary of English v.0.48:

free-for-all \free-for-all\ n.
   1. a noisy and disordered fight conducted without rules.

   Syn: brawl.
        [WordNet 1.5]

   2. Hence: Any vigorous competition in which anyone can
      compete, with few or no rules, and in which the winner is
      unpredictable; as, when they began to distribute the free
      food, the orderly line of hungry recipients degenerated
      into a free-for-all.
      [PJC]

WordNet (r) 3.0 (2006):

free-for-all
    n 1: a noisy fight in a crowd [syn: brawl, free-for-all]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "free-for-all":
   Bedlam let loose, ado, affray, bedlam, blast, bobbery, bother,
   brawl, broil, brouhaha, charivari, chirm, clamor, clangor, clap,
   clatter, commotion, din, discord, disturbance, donnybrook,
   donnybrook fair, drunken brawl, dustup, embroilment, fight, flap,
   foofaraw, fracas, fray, fuss, hassle, hell broke loose,
   helter-skelter, howl, hubbub, hue and cry, hullabaloo, jangle,
   knock-down-and-drag-out, loud noise, melee, noise,
   noise and shouting, outcry, pandemonium, pell-mell, pother, racket,
   rampage, rattle, rhubarb, riot, roar, rough-and-tumble, roughhouse,
   row, ruckus, ruction, rumble, rumpus, scramble, scrimmage, shindy,
   shivaree, stir, thunder, thunderclap, tintamarre, to-do, trouble,
   tumult, turmoil, uproar