The Collaborative International Dictionary of English v.0.48:

Harmonica \Har*mon"i*ca\ (-[i^]*k[.a]), n. [Fem. fr. L.
   harmonicus harmonic. See Harmonic, n. ]
   1. A musical instrument, consisting of a series of
      hemispherical glasses which, by touching the edges with
      the dampened finger, give forth the tones; it is now
      called the glass harmonica, to distinguish it from the
      common harmonica, formerly called the harmonicon.
      [1913 Webster]

   2. A toy instrument of strips of glass or metal hung on two
      tapes, and struck with hammers.
      [1913 Webster]

   3. A small wind musical instrument shaped like a flat bar
      with holes along the thin edges, held in the hand and
      producing notes from multiple vibrating reeds arranged
      inside along its length; it was formerly called the
      harmonicon. See harmonicon.
      [PJC]