-_jə̇st noun
( -s )
Etymology: New Latin synergista, from Greek synergos + Latin -ista -ist
1. : one who holds the doctrine of synergism
2. : an agent that increases the effectiveness of another agent when combined with it: as
a. : a drug that acts in synergism with another
b. : a substance (as piperonyl butoxide) that increases the effectiveness of an insecticide or other pesticide
c. : a substance that increases the activity of an antioxidant ; especially : such a substance (as phosphoric acid) that is not an antioxidant by itself
3. : an organ (as a muscle) that acts in concert with another to enhance its effect — compare agonist