Antonyms of noun antagonist

2 of 3 senses of antagonist

Sense 1
adversary, antagonist, opponent, opposer, resister -- (someone who offers opposition)
       Antonym of agonist (Sense 2)
      => agonist -- (someone involved in a contest or battle (as in an agon))

Sense 3
antagonist -- (a drug that neutralizes or counteracts the effects of another drug)
       Antonym of synergist (Sense 1)
      => synergist -- (a drug that augments the activity of another drug)

Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun antagonist

3 senses of antagonist

Sense 1
adversary, antagonist, opponent, opposer, resister -- (someone who offers opposition)
       => person, individual, someone, somebody, mortal, soul -- (a human being; "there was too much for one person to do")

Sense 2
antagonist -- (a muscle that relaxes while another contracts; "when bending the elbow the triceps are the antagonist")
       => antagonistic muscle -- ((physiology) a muscle that opposes the action of another; "the biceps and triceps are antagonistic muscles")

Sense 3
antagonist -- (a drug that neutralizes or counteracts the effects of another drug)
       => drug -- (a substance that is used as a medicine or narcotic)