The major (accent on "o") is a polysemantic word, derived from the English "Major" (major, major) and having at least two basic meanings in the Russian language:
In music, "major" means an increase in tonality. In "major" melodies, as a rule, there is much more positive and drive than in "minor" melodies.
In colloquial speech "major" is the son of a rich or influential father, bathing in luxury and leading a dissolute life. The group DDT has an old song "Boys-majors", making fun of such a contingent.
The major is in the list: Slang