enharmonic

Enharmonic \En`har*mon"ic\ ([e^]n`h[.a]r*m[o^]n"[i^]k),
Enharmonical \En`har*mon"ic*al\ ([e^]n`h[.a]r*m[o^]n"[i^]*kal),
   a. [Gr. 'enarmoniko`s, 'enarmo`nios fitting, accordant; 'en
   in + "armoni`a harmony: cf. F. enharmonique.]
   1. (Anc. Mus.) Of or pertaining to that one of the three
      kinds of musical scale (diatonic, chromatic, enharmonic)
      recognized by the ancient Greeks, which consisted of
      quarter tones and major thirds, and was regarded as the
      most accurate.
      [1913 Webster]

   2. (Mus.)
      (a) Pertaining to a change of notes to the eye, while, as
          the same keys are used, the instrument can mark no
          difference to the ear, as the substitution of A[flat]
          for G[sharp].
      (b) Pertaining to a scale of perfect intonation which
          recognizes all the notes and intervals that result
          from the exact tuning of diatonic scales and their
          transposition into other keys.
          [1913 Webster]