antagonist

Science Dictionary
antagonist   (ān-tāg'ə-nĭst)  Pronunciation Key 
  1. A muscle that opposes the action of another muscle, as by relaxing while the other one contracts, thereby producing smooth, coordinated movement.

  2. A chemical substance, such as a drug, that interferes with the physiological action of another substance, especially by combining with and blocking its nerve receptor. Compare agonist.


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