Definition of "Major" :
noun: the principal field of study of a student at a university
"Her major is linguistics."
noun: a commissioned military officer in the United States Army or Air Force or Marines; below lieutenant colonel and above captain
noun: a university student who is studying a particular field as the principal subject
"She is a linguistics major."
noun: British statesman who was prime minister from 1990 until 1997 (born in 1943)
verb: have as one's principal field of study
"She is majoring in linguistics."
adjective: greater in number or size or amount
"A major portion (a majority) of the population."
adjective: greater in scope or effect
"A major contribution."
adjective: of full legal age
adjective: (of a scale or mode) having half steps between the third and fourth degrees and the seventh and eighth degrees
adjective: of the field of academic study in which one concentrates or specializes
"His major field was mathematics."
adjective: of greater importance or stature or rank
"A major artist."
adjective: of greater seriousness or danger
"A major earthquake."
adjective: of the elder of two boys with the same family name