Definition of "antagonist" in English

noun

1. An opponent or enemy.

2. One who antagonizes or stirs.

3. (biochemistry) A chemical that binds to a receptor but does not produce a physiological response, blocking the action of other agonist chemicals, such as endogenous chemical messengers.

   • 2001: The calcium antagonists represent one of the top ten classes of prescription drugs in terms of commercial value, with worldwide sales of nearly $10 billion in 1999. — Leslie Iversen, Drugs: A Very Short Introduction (Oxford 2001, p. 41)

4. (authorship) The main character or force opposing the protagonist in a literary work or drama.

5. (anatomy) A muscle that acts in opposition to another.

   • A flexor, which bends a part, is the antagonist of an extensor, which extends it.