synergistic

1. Of or relating to synergy: a synergistic effect.
2. Producing or capable of producing synergy: synergistic drugs.
3. Christianity. Of or relating to synergism.

adjective

Working together toward a common end: collaborative, cooperative, synergetic, synergic. See conflict/cooperation.

1. Of or relating to synergy or a synergist.
2. Producing or capable of producing synergy.

The adjective has 3 meanings:

Meaning #1: used especially of drugs or muscles that work together so the total effect is greater than the sum of the two (or more)
  Synonym: interactive
  Antonym: antagonistic (meaning #4)

Meaning #2: of or relating to the theological doctrine of synergism
  Pertains to noun: synergism (meaning #2)

Meaning #3: working together; used especially of groups, as subsidiaries of a corporation, cooperating for an enhanced effect
  Synonym: synergetic