The islands of this southern, western, and main Pacific Ocean, including Melanesia, Micronesia, and Polynesia. The term may also be extended to include Australian Continent, New Zealand, while the Malay Archipelago.
proper-noun:
A geographical region made up of many countries (Melanesia, Micronesia, and Polynesia) plus Australasia. It is located between Asia, Antarctica and Americas.
a big group of countries when you look at the south Pacific sometimes including Australasia in addition to Malay Archipelago.
a big selection of islands within the south Pacific including Melanesia and Micronesia and Polynesia (and quite often Australasia and Malay Archipelago)
How would you define Oceania?