means A large-scale musical composition for orchestra, usually in several movements, in which many instruments are woven into a single unfolding whole.

from From Greek 'symphōnia,' a marriage of 'syn-' (together) and 'phōnē' (sound or voice) — literally 'sounding together.' It passed through Latin 'symphonia' and Old French before reaching English, where for centuries it could mean any pleasing concord of sounds, or even an instrument that made them. Only later did it settle into its grand modern sense: not just sounds agreeing, but a whole architecture of agreement.