The nationality belonging to someone with citizenship in the country of Australia.
Commonly stereotyped by the likes of The Simpsons, Monty Python and teenagers, as having thick accents, riding around in kangaroos all day and having little to no infrastructure, living out in the desert.
Australia is home to many fine cities, including Melbourne which was allegedly awarded the "world's most livable city" title at some point recently.
Derek: yo baxter, check out this australian dude
Baxter: i say old chap, he's quite the commoner, with his khaki rags.
Bruce: G'day, do you blokes know a good place to eat?
Baxter: ah yes, there's one near here. it's down the street, take a ha'penny and follow the locomotive track.