The Collaborative International Dictionary of English v.0.48:

major diatonic scale \major diatonic scale\ n. (Mus.),
   The natural diatonic scale, which has semitones between the
   third and fourth, and seventh and eighth notes, and whole
   tones between the other notes; the scale of the major mode,
   of which the third is major; also called major scale. See
   Scale, and Diatonic.
   [1913 Webster + WordNet 1.5]

WordNet (r) 3.0 (2006):

major diatonic scale
    n 1: a diatonic scale with notes separated by whole tones except
         for the 3rd and 4th and 7th and 8th [syn: major scale,
         major diatonic scale]