a commissioned military officer ranking next below a lieutenant colonel and next above a captain.

one of superior rank, ability, etc., in a specified class.

Education .

a subject or field of study chosen by a student to represent his or her principal interest and upon which a large share of his or her efforts are concentrated

History was my major at college.

a student engaged in such study.

a person of full legal age ( opposed to minor ).

Music . a major interval, chord, scale, etc.

the majors,

Sports . the major leagues

He coached in the majors as well as in the minors.

the companies or organizations that lead or control a particular field of activity

the oil majors.

greater in size, extent, or importance

the major part of the town.

great, as in rank or importance

a major political issue; a major artist.

serious or risky

a major operation.

of or pertaining to the majority

the major opinion.

of full legal age.

Music .

(of an interval) being between the tonic and the second, third, sixth, or seventh degrees of a major scale

a major third; a major sixth.

(of a chord) having a major third between the root and the note next above it.

pertaining to the subject in which a student takes the most courses

Her major field is English history.

( initial capital letter ) (of one of two male students in an English public school who have the same surname) being the elder or higher in standing

Hobbes Major is not of a scientific bent.

to follow a major course of study

He is majoring in physics.

adjective

lesser , little , minor , small , insignificant , unimportant

adjective

above , better , big , chief , considerable , dominant , elder , exceeding , extensive , extreme , greater , hefty , higher , large , larger , large-scale , leading , main , most , oversized , primary , senior , sizable , superior , supreme , ultra , upper , uppermost , critical , crucial , dangerous , grave , great , grievous , heavyweight , influential , life and death , major-league , meaningful , notable , outstanding , overshadowing , preeminent , principal , radical , serious , significant , star , stellar , top , vital , weighty , blue-chip , capital , cardinal , first , foremost , key , number one , paramount , premier , prime , important , predominant