Definition of Australia from the Oxford Advanced Learner's Dictionary

a large island country and continent in the south-west Pacific Ocean. Its capital city is Canberra and its official language is English. The first inhabitants of Australia were the Aborigines, who now form only about 1.5% of the population. In 1770 the country was visited by Captain James Cook, and in the 18th and 19th centuries it was used by the British as a place to send criminals. Many of Australia's present inhabitants are descended from British people. It is now independent from Britain, although it remains a member of the Commonwealth. Most of the population live on or near the coast in the east and south of the country, and there are large areas in the west, north and centre of the country that have very few inhabitants. The climate is generally warm. Australian culture is popular in Britain. A number of Australian programmes, including soap operas such as Neighbours, appear regularly on British television. A popular informal name for Australia is 'Down Under'. see also Botany Bay See related entries: Countries and continents
See the Oxford Advanced American Dictionary entry: Australia