Definitions of major:

• noun:   the principal field of study of a student at a university

  Example: "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

  Example: "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

  Example: "She is majoring in linguistics"

• adjective:   greater in number or size or amount

  Example: "A major portion (a majority) of the population"

• adjective:   greater in scope or effect

  Example: "A major contribution"

• adjective:   of full legal age

  Example: "Major children"

• adjective:   of a scale or mode

  Example: "Major scales"

• adjective:   of the field of academic study in which one concentrates or specializes

  Example: "His major field was mathematics"

• adjective:   of greater importance or stature or rank

  Example: "A major artist"

• adjective:   of greater seriousness or danger

  Example: "A major earthquake"

• name:  A male given name (rare: 1 in 14285 males; popularity rank in the U.S.: #826)
• name:  A surname (common: 1 in 11111 families; popularity rank in the U.S.: #1441)