Definition from Wiktionary, the free dictionary
See also Antagonist
antagonist (plural antagonists)
- An opponent or enemy.
- One who antagonizes or stirs.
- (biochemistry) A chemical that binds to a receptor but does not produce a physiological response, blocking the action of agonist chemicals.
- 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)
- The main character or force opposing the protagonist in a literary work or drama.
Related terms 
one who antagonizes