Synonyms for Major:

adj.

bigger (adjective)
above, superior, ultra, upper, extreme, leading, supreme, chief, better, dominant, primary, larger, higher, main.
important (adjective)
influential, serious, outstanding, heavyweight, crucial, great, star, main, significant, important, stellar, vital, dominant, central, fundamental, top, principal.

n.

primary, higher, ultra, CDR, aide-de-camp, brigadier general, captain, larger, co, dominant, brigadier, col, above, superior, upper, chief of staff, over, adjutant, colonel, extreme. designated hitter, important, big league, batter, major league, heavyweight, bigtime, catcher, the American League, bush-league, the Golden Glove Awards, the Cy Young Award, ball game, blue-chip, All-Star game. chief, BMP, capital, Big Man on Campus, foremost, alum, auditor, dropout, top, main, premier, campus, fresher, cardinal, key, paramount, COED, number one, prime, principal, alumna, alumnus, first. correspondence course, class, apprenticeship, day school, course, concentration, articles, ed, doctoral, crash course. elementary, predominant, supreme, basic. emphasize, count, come before, matter, figure, dominate, loom large, signify, predominate, lie at the heart of something. greater (noun)
above, higher, upper, dominant, superior, primary, better.
important (noun)
important, significant.
major (noun)
star, better, outstanding, stellar, great, starring, prima, leading.

Other synonyms:

cardinal, blue-chip, big league, principal, chromatic, fundamental, bigtime, diatonic, major league, important, premier. foremost, leading, primary, key, paramount, main, heavyweight. course. first, prime. tonic. sharp. flat. Other relevant words:
larger, first, apprenticeship, catcher, doctoral, chromatic, crucial, chief, alum, big league, CDR, colonel, col, major league, matter, aide-de-camp, cardinal, auditor, dropout, foremost, captain, adjutant, key, bigtime, better, higher, dominate, principal, number one, heavyweight, significant, articles, diatonic, vital, alumna, figure, premier, extreme, supreme, elementary, batter, ed, predominant, basic, campus, signify, emphasize, count, ultra, flat, above, predominate, COED, dominant, BMP, serious, course, capital, important, influential, sharp, concentration, over, top, alumnus, chief of staff, superior, brigadier, brigadier general, class, upper, primary, main, prime, tonic, fundamental, central, paramount, fresher.