1. Concordant; musical; consonant; as, harmonic sounds. Harmonic twang! of leather, horn, and brass. (Pope)
2. Relating to harmony, as melodic relates to melody; harmonious; especially, relating to the accessory sounds or overtones which accompany the predominant and apparent single tone of any string or sonorous body. Harmonic interval, the distance between two notes of a chord, or two consonant notes.
3. (Science: mathematics) Having relations or properties bearing some resemblance to those of musical consonances; said of certain numbers, ratios, proportions, points, lines. Motions, and the like.
harmonical mean, the chord of a note with its third and fifth; the common chord.
Origin: L. Harmonicus, gr.; cf. F. Harmonique.