antagonist
1. [ noun ] someone who offers opposition
Synonyms: opponent adversary resister opposer
Related terms: agonist person enemy dueler Luddite Antichrist withstander oppose resist oppose
2. [ noun ] (pharmacology) a drug that neutralizes or counteracts the effects of another drug
Related terms: synergist drug narcotic_antagonist estrogen_antagonist
3. [ noun ] (anatomy,zoology) a muscle that relaxes while another contracts
Examples:

"when bending the elbow the triceps are the antagonist"

Related terms: antagonistic_muscle
Similar spelling:   antagonistic
  antagonism
  antagonise
  antagonize
  antagonizing
  Antigonus
  Antigonia