In USA English, an 'expat' typically means someone who has moved to another country and lives there the vast majority of the time, if not always. They do little to become part of the society where they live - often they do the opposite. They live in expat enclaves where they do the best they can to make things just like where they came from, except cheaper and with a warmer climate. It's small-scale colonialism facilitated by money and white privilege instead of guns.