The Collaborative International Dictionary of English v.0.48:

Calliope \Cal*li"o*pe\ (k[a^]l*l[imac]"[-o]*p[-e]), n. [L.
   Calliope, Gr. Kallio`ph, lit, the beautiful-voiced; pref.
   kalli- (from kalo`s beautiful) + 'o`ps, 'opo`s, voice.]
   1. (Class. Myth.) The Muse that presides over eloquence and
      heroic poetry; mother of Orpheus, and chief of the nine
      Muses.
      [1913 Webster]

   2. (Astron.) One of the asteroids. See Solar.
      [1913 Webster]

   3. A musical instrument consisting of a series of steam
      whistles, toned to the notes of the scale, and played by
      keys arranged like those of an organ. It is sometimes
      attached to steamboat boilers.
      [1913 Webster]

   4. (Zool.) A beautiful species of humming bird (Stellula
      Calliope) of California and adjacent regions.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Calliope
    n 1: (Greek mythology) the Muse of epic poetry
    2: a musical instrument consisting of a series of steam whistles
       played from a keyboard [syn: calliope, steam organ]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "calliope":
   Hammond organ, Mark, baroque organ, bazooka, calliophone,
   choralcelo, electric organ, electro-pneumatic organ, harmonium,
   hedgehog, hydraulic organ, launch pad, launching pad,
   launching platform, launching tube, melodeon, melodica, mousetrap,
   orchestrelle, organ, organophone, pipe organ, projector,
   reed organ, seraphine, silo, steam organ, symphonion,
   tracker-action organ, tubular-pneumatic organ, vocalion