When something is synergistic, it means various parts are working together to produce an enhanced result. If you’ve just heard a synergistic symphony, the musicians must have played very well together.
You’ve probably heard the phrase “more than the sum of its parts.” The prefix syn- means "together with" or "united." When synergistic parts work together, they accomplish more than they could alone. Synergetic is often used to describe the effect of drugs working together — where one drug increases the other’s effectiveness. Synergistic can also describe the cooperative efforts of several people working together — like a team of superheroes fighting crime.