The Collaborative International Dictionary of English v.0.48:
Major \Ma"jor\, [L. major, compar. of magnus great: cf. F.
majeur. Cf. Master, Mayor, Magnitude, More, a.]
1. Greater in number, quantity, or extent; as, the major part
of the assembly; the major part of the revenue; the major
part of the territory.
2. Of greater dignity; more important. --Shak.
3. Of full legal age; adult. [Obs.]
4. (Mus.) Greater by a semitone, either in interval or in
difference of pitch from another tone.
Major key (Mus.), a key in which one and two, two and
three, four and five, five and six and seven, make major
seconds, and three and four, and seven and eight, make
Major offense (Law), an offense of a greater degree which
contains a lesser offense, as murder and robbery include
Major scale (Mus.), the natural diatonic scale, which has
semitones between the third and fourth, and seventh and
fourth, and seventh and eighth degrees; the scale of the
major mode, of which the third is major. See Scale, and
Major second (Mus.), a second between whose tones is a
difference in pitch of a step.
Major sixth (Mus.), a sixth of four steps and a half step.
In major keys the third and sixth from the key tone are
major. Major keys and intervals, as distinguished from
minors, are more cheerful.
Major third (Mus.), a third of two steps.