主要的；重要的；大的very large or important
a major road
major international companies
to play a major role in sth
We have encountered major problems.
There were calls for major changes to the welfare system.
Never mind─it's not major.
大调的based on a scale (= a series of eight notes) in which the third note is two whole tones/steps higher than the first note
the key of D major
（课程）主修的related to sb's main subject of study in college
少校an officer of fairly high rank in the army or the US air force
He's a major in the US army.
主修课程；专业课the main subject or course of a student at college or university
Her major is French.
主修学生；主修生a student studying a particular subject as the main part of their course
She's a French major.
大联盟the major leagues