The Collaborative International Dictionary of English v.0.48:

antitrust \antitrust\ adj.
   1. opposed to trusts, monopolies, or other large combinations
      of business or capital which threaten fair competition;
      designed to protect trade and commerce from unfair
      business practices; -- of laws and regulations.

   Syn: antimonopoly.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

antitrust
    adj 1: of laws and regulations; designed to protect trade and
           commerce from unfair business practices [syn:
           antimonopoly, antitrust]