Source : Webster's Revised Unabridged Dictionary (1913)

Polyphony \Po*lyph"o*ny\, n. [Gr. ?.]
   1. Multiplicity of sounds, as in the reverberations of an
      echo.

   2. Plurality of sounds and articulations expressed by the
      same vocal sign.

   3. (Mus.) Composition in mutually related, equally important
      parts which share the melody among them; contrapuntal
      composition; -- opposed to homophony, in which the melody
      is given to one part only, the others filling out the
      harmony. See {Counterpoint}.

Source : WordNet®

polyphony
     n : music arranged in parts for several voices or instruments
         [syn: {polyphonic music}, {concerted music}] [ant: {monophony},
          {monophony}]