Definitions of harmonic:

• noun:   a tone that is a component of a complex sound
• adjective:   of or relating to harmony as distinct from melody and rhythm

  Example: "Subtleties of harmonic change and tonality- Ralph Hill"

• adjective:   of or relating to the branch of acoustics that studies the composition of musical sounds

  Example: "The sound of the resonating cavity cannot be the only determinant of the harmonic response"

• adjective:   relating to vibrations that occur as a result of vibrations in a nearby body
• adjective:   involving or characterized by harmony