har·mon·ic / härˈmänik/ • adj. 1. of, relating to, or characterized by musical harmony: a basic four-chord harmonic sequence. ∎ Mus. relating to or denoting a harmonic or harmonics.2. Math. of or relating to a harmonic progression. ∎  Physics of or relating to component frequencies of a complex oscillation or wave. ∎  Astrol. using or produced by the application of a harmonic: harmonic charts.• n. 1. Mus. an overtone accompanying a fundamental tone at a fixed interval, produced by vibration of a string, column of air, etc., in an exact fraction of its length. ∎  a note produced on a musical instrument as an overtone, e.g., by lightly touching a string while sounding it.2. Physics a component frequency of an oscillation or wave. ∎  Astrol. a division of the zodiacal circle by a specified number, used in the interpretation of a birth chart.DERIVATIVES: har·mon·i·cal·ly / -ik(ə)lē/ adv.

harmonic A frequency which is a whole multiple of the fundamental frequency; thus the second harmonic has twice the fundamental frequency, the third harmonic three times, etc.