An overtone is a tone that is present in the sounding of a fundamental, due to the physics of the production of musical tones. A component of a complex tone having a frequency higher than the fundamental.

 

A harmonic overtone is a frequency that is an integer multiple of the frequency of the fundamental (as opposed to inharmonic overtones, which are non-integer mutliples).

 

On a wind instrument, overtones are produced by overblowing.