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]