Dictionary.net

One who holds the doctrine of synergism.

A remedy which has an action similar to that of another remedy, and hence increases the efficiency of that remedy when combined with it.

A muscle or agent which acts with another.

Cooperating; as a n., a muscle that cooperates with another also a drug that intensifies the action of another drug.

n. [Greek] One of a party of Lutheran divines in the end of the 16th century, who taught that divine grace requires a concurrent or co-operating act of man's free will in the work of regeneration ; a kind of semi-Pelagian.