It's a North American "wynalazek". Not sure if it's common in the UK and, frankly, I don't feel like looking it up.
Oh, and there is also a "minor" and a "double major".
major (SPECIAL SUBJECT) [Show phonetics]
noun [C] US
the most important subject that a college or university student is studying, or the student himself or herself:
What is your major, English or French?
She was a philosophy major at an Ivy League college.
major in sth verb US
to study something as your main subject at university:
She majored in philosophy at Harvard.