The Collaborative International Dictionary of English v.0.48:

Overtone \O"ver*tone`\, n. [A translation of G. oberton. See
   Over, Tone.] (Mus.)
   One of the harmonics faintly heard with and at a higher
   frequency than a fundamental tone as it dies away, produced
   by some aliquot portion of the vibrating sting or column of
   air which yields the fundamental tone; one of the natural
   harmonic scale of tones, as the octave, twelfth, fifteenth,
   etc.; an aliquot or "partial" tone; a harmonic. See
   Harmonic, and Tone. --Tyndall.
   [1913 Webster]

WordNet (r) 3.0 (2006):

overtone
    n 1: (usually plural) an ulterior implicit meaning or quality;
         "overtones of despair"
    2: a harmonic with a frequency that is a multiple of the
       fundamental frequency [syn: overtone, partial, partial
       tone]