Synonyms for Synergistic (same or very similar meaning)
WordNet sense 1 (used especially of drugs or muscles that work together so the total effect is greater than the sum of the two (or more)):
interactiveWordNet sense 2 (working together; used especially of groups, as subsidiaries of a corporation, cooperating for an enhanced effect):
synergeticWordNet sense 3 (done with or working with others for a common purpose or benefit):
cooperativeFrom the ODE community, based on WordNetadd/edit