har·mon·ic 
(här-mŏnĭk)
(här-mŏnĭk)adj.
1.
a. Of or relating to harmony.
b. Pleasing to the ear: harmonic orchestral effects.
c. Characterized by harmony: a harmonic liturgical chant.
2. Of or relating to harmonics.
3. Integrated in nature.
n.
1.
a. Any of a series of musical tones whose frequencies are integral multiples of the frequency of a fundamental tone.
b. A tone produced on a stringed instrument by lightly touching an open or stopped vibrating string at a given fraction of its length so that both segments vibrate. Also called overtone, partial, partial tone.
2. harmonics (used with a sing. verb) The theory or study of the physical properties and characteristics of musical sound.
3. Physics Any of a series of periodic waves whose frequencies are integral multiples of a fundamental frequency.
[Latin harmonicus, from Greek harmonikos, from harmoniā, harmony; see HARMONY.]
har·moni·cal·ly adv.
harmonicVisual representation of harmonics in the periodic motion of a vibrating guitar string. First (or fundamental) harmonic (top), second harmonic (center), and sixth harmonic (bottom).