Source : Webster's Revised Unabridged Dictionary (1913)

Opera \Op"er*a\, n. [It., fr. opera work, composition, opposed
   to an improvisation, fr. L. opera pains work, fr. opus,
   operis, work, labor: cf. F. op['e]ra. See {Operate}.]
   1. A drama, either tragic or comic, of which music forms an
      essential part; a drama wholly or mostly sung, consisting
      of recitative, arials, choruses, duets, trios, etc., with
      orchestral accompaniment, preludes, and interludes,
      together with appropriate costumes, scenery, and action; a
      lyric drama.

   2. The score of a musical drama, either written or in print;
      a play set to music.

   3. The house where operas are exhibited.

   {Op['e]ra bouffe} [F. op['e]ra opera + bouffe comic, It.
      buffo], {Opera buffa} [It.], light, farcical, burlesque
      opera.

   {Opera box}, a partially inclosed portion of the auditorium
      of an opera house for the use of a small private party.

   {Op['e]ra comique} [F.], comic or humorous opera.

   {Opera flannel}, a light flannel, highly finished. --Knight.

   {Opera girl} (Bot.), an East Indian plant ({Mantisia
      saltatoria}) of the Ginger family, sometimes seen in
      hothouses. It has curious flowers which have some
      resemblance to a ballet dancer, whence the popular name.
      Called also {dancing girls}.

   {Opera glass}, a short telescope with concave eye lenses of
      low power, usually made double, that is, with a tube and
      set of glasses for each eye; a lorgnette; -- so called
      because adapted for use at the opera, theater, etc.

   {Opera hat}, a gentleman's folding hat.

   {Opera house}, specifically, a theater devoted to the
      performance of operas.

   {Opera seria} [It.], serious or tragic opera; grand opera.