Source : Webster's Revised Unabridged Dictionary (1913)

Apotome \A*pot"o*me\, n. [Gr. ? a cutting off, fr. ? to cut off;
   ? from + ? to cut.]
   1. (Math.) The difference between two quantities
      commensurable only in power, as between [root]2 and 1, or
      between the diagonal and side of a square.

   2. (Mus) The remaining part of a whole tone after a smaller
      semitone has been deducted from it; a major semitone.
      [Obs.]