The Collaborative International Dictionary of English v.0.48:

Symphony \Sym"pho*ny\, n.; pl. Symphonies. [F. symphonie (cf.
   It. sinfonia), L. symphonia, Gr. ?; sy`n with + ? a sound,
   the voice. See Phonetic.]
   1. A consonance or harmony of sounds, agreeable to the ear,
      whether the sounds are vocal or instrumental, or both.
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            The trumpets sound,
            And warlike symphony in heard around. --Dryden.
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   2. A stringed instrument formerly in use, somewhat resembling
      the virginal.
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            With harp and pipe and symphony.      --Chaucer.
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   3. (Mus.)
      (a) An elaborate instrumental composition for a full
          orchestra, consisting usually, like the sonata, of
          three or four contrasted yet inwardly related
          movements, as the allegro, the adagio, the minuet and
          trio, or scherzo, and the finale in quick time. The
          term has recently been applied to large orchestral
          works in freer form, with arguments or programmes to
          explain their meaning, such as the "symphonic poems"
          of Liszt. The term was formerly applied to any
          composition for an orchestra, as overtures, etc., and
          still earlier, to certain compositions partly vocal,
          partly instrumental.
      (b) An instrumental passage at the beginning or end, or in
          the course of, a vocal composition; a prelude,
          interlude, or postude; a ritornello.
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