semitone Meaning, Definition & Usage

  1. noun the musical interval between adjacent keys on a keyboard instrument
    half step.

WordNet

Sem"i*tone noun
Etymology
Pref. semi- + tone. CF. Hemitone.
Definitions
  1. (Mus.) Half a tone; -- the name commonly applied to the smaller intervals of the diatonic scale. ✍ There is an impropriety in the use of this word, and half step is now preferred. See Tone. J. S. Dwight.

Webster 1913