antagonist
antagonist (an*tag"o*nist) , noun
[Latin antagonista, Greek 'antagwnisth`s; 'anti` against + 'agwnisth`s combatant, champion, from 'agwni`zesqai: compare French antagoniste. See Antagonism.]
1.
One who contends with another, especially in combat; an adversary; an opponent.
Antagonist of Heaven's Almighty King.
Our antagonists in these controversies.
2.
(Anatomy) A muscle which acts in opposition to another; as a flexor, which bends a part, is the antagonist of an extensor, which extends it.
3.
(Medicine) A substance which opposes the actions of another substance in the body, especially a drgu that counteracts the effects of another drug.
Antagonist , adjective
Antagonistic; opposing; counteracting; as, antagonist schools of philosophy.