A term given to someone who travels a lot, specifically to other countries (hence the word 'global'), for their studies or for work experience. Supposed to be used in a joking manner.
Ivan: I got my time-off approved by my boss.
Amy: Oh, a holiday?
Ivan: No, I've been awarded a scholarship to study in France/Germany/Japan/Malaysia/America/Italy
Amy: Wow! Another one? You go to so many places. Haha, you never stay put, you global slut.
Ivan: Haha, yeah, well when the opportunity presents itself I gotta take advantage of it.