Source : Webster's Revised Unabridged Dictionary (1913)

Harmonic \Har*mon"ic\, Harmonical \Har*mon"ic*al\, a. [L.
   harmonicus, Gr. ?; cf. F. harmonique. See {Harmony}.]
   1. Concordant; musical; consonant; as, harmonic sounds.

            Harmonic twang! of leather, horn, and brass. --Pope.

   2. (Mus.) Relating to harmony, -- as melodic relates to
      melody; harmonious; esp., relating to the accessory sounds
      or overtones which accompany the predominant and apparent
      single tone of any string or sonorous body.

   3. (Math.) Having relations or properties bearing some
      resemblance to those of musical consonances; -- said of
      certain numbers, ratios, proportions, points, lines.
      motions, and the like.

   {Harmonic interval} (Mus.), the distance between two notes of
      a chord, or two consonant notes.

   {Harmonical mean} (Arith. & Alg.), certain relations of
      numbers and quantities, which bear an analogy to musical
      consonances.

   {Harmonic motion},

Source : WordNet®

harmonical
     adj : involving or characterized by harmony [syn: {consonant}, {harmonic},
            {harmonized}, {harmonised}, {in harmony}]