- It has one very technical use in astronomy, particularly in the study of the planet Mars: the Amazonis Planitia, a large smooth plain, has given its name to one of the epochs of Martian geology, the Amazonian, hypothesized as lasting from about 1,800,000,000 or 3,000,000,000 years ago to the present day. Like various geological epochs on Earth, it is conveniently divided into three sub-epochs, the Lower, Middle and Upper Amazonian.
- In more general use, Amazonian may be used descriptively ('adjectivally') about any of the meanings listed at Amazon - although only jocularly about the internet retailer. However
AWE recommends writers of academic English to reserve its use to the geographical -
to describe things found in South America, and strictly only those found within the boundaries of the Amazon river basin, as in 'amazonian species' and 'the amazonian water system'.
If you are seeking an adjective for the mythical race of women warriors (or any of the figurative extensions thereof), it is quite conventional and perfectly proper to use Amazon itself epithetically - as an adjective.