The Nullarbor Plain does not have a specific coastline. It's a vast, flat, and arid plateau located in southwestern Australia.

Here's why:

* The Nullarbor Plain borders the Great Australian Bight. This is a large, curved indentation in the southern coastline of Australia.

* The plain itself doesn't reach the ocean. There is a steep cliff edge that drops directly to the sea, making it a dramatic and unique coastal feature.

So, while the Nullarbor Plain is near the southern coastline, it's not technically considered a part of it.