Meaning of MAJOR in English

I. ma ‧ jor 1 S1 W1 AC /ˈmeɪdʒə $ -ər/ BrE AmE adjective

[ Date: 1200-1300 ; Language: Latin ; Origin: 'larger, greater' , from magnus 'large, great' ]

1 . [usually before noun] having very serious or worrying results OPP minor :

There is a major problem with parking in London.

The loss of their goalkeeper through injury was a major setback for the team.

He underwent major heart surgery recently.

It could have sparked a major confrontation.

2 . [usually before noun] very large or important, when compared to other things or people of a similar kind OPP minor

major role/part/factor etc

Britain played a major role in the negotiations.

There are two major political parties in the US.

The government’s major concern is with preventing road accidents.

Smoking is one of the major causes of cancer.

the major developments in computer technology

a major road

3 . [not before noun] American English spoken very important:

This is major? You got me out of bed for this?

4 . a major ↑ key is based on a musical ↑ scale in which there are ↑ semitone s between the third and fourth and the seventh and eighth notes ⇨ minor :

a symphony in D major

II. major 2 BrE AmE noun [countable]

1 . an officer of middle rank in the British or US army or ↑ Marines , or in the US air force ⇨ ↑ drum major

2 . especially American English the main subject that a student studies at college or university:

Her major is history.

3 . American English someone studying a particular subject as their main subject at college or university:

She’s a history major.

4 . the majors [plural] the ↑ Major Leagues

III. major 3 BrE AmE verb

major in something phrasal verb

especially American English to study something as your main subject at college or university:

He’s majoring in Political Science.

major on something phrasal verb

especially British English to pay particular attention to one subject or thing:

The company is planning to major on offering the machines we need.

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.