antagonist (n.)

  1. someone who offers opposition

    [ Syn: adversary , opponent , opposer , resister ]

  2. a muscle that relaxes while another contracts; when bending the elbow the triceps are the antagonist'

  3. a drug that neutralizes or counteracts the effects of another drug

The dictionary is based on the WordNet Electronic Lexical Database.
WordNet 3.0 Copyright 2011 by Princeton University. All rights reserved.