Definition of major :
1. A mayor.
2. A person of full age.
3. An officer next in rank above a captain and next below a lieutenant colonel; the lowest field officer.
4. Greater by a semitone, either in interval or in difference of pitch from another tone.
5. 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.
6. Of full legal age.
7. Of greater dignity; more important.
8. That premise which contains the major term. It its the first proposition of a regular syllogism; as: No unholy person is qualified for happiness in heaven [ the major]. Every man in his natural state is unholy [ minor]. Therefore, no man in his natural state is qualified for happiness in heaven [ conclusion or inference].
Cdr., blue-chip, great, flat, All-Star game, concentration, Big Man on Campus, monumental, tonic, adjutant, bush league, healthy, basic, earth-shattering, sizable, chief, prime, correspondence course, star, starring, big, consequential, alumna, class, dominant, alumnus, C.O., crash course, heavyweight, chief of staff, better, course, much, superior, momentous, the Cy Young Award, fresher, minor, outstanding, respectable, count, lie at the heart of something, capital, chromatic, designated hitter, bmp, upper, top, eventful, foremost, Col., meaningful, supreme, key, dropout, emphasize, colonel, auditor, largish, the Golden Glove Awards, elementary, good, cardinal, captain, historic, number one, coed, figure, come before, higher, doctoral, earthshaking, leading, apprenticeship, tidy, campus, day school, handsome, premier, ed., brigadier-general, batter, ball game, senior, biggish, big-league, above, ultra, goodly, major-league, tectonic, stellar, brigadier, over, loom large, dominate, signify, predominant, extreme, substantive, catcher, articles, substantial, first, larger, the American League, sharp, material, predominate, bigtime, alum, primary, diatonic, weighty, matter, prima, aide-de-camp, paramount
important (part of speech: adjective)