- generally, the islands of the SW Pacific
- Australia, New Zealand, New Guinea, the Malay Archipelago, and all islands south of the equator and between E longitudes 100 and 180
- The islands of the southern Pacific Ocean, including Australia, New Zealand, and New Guinea.
- Broadly, all of Oceania.
This is an ambiguous term, whose precise meaning varies considerably depending on its field of use
australasia - Investment & Finance Definition
Australia and the Far East.