There isn't a single universally accepted alternative name for coastal plains. However, depending on the specific context, you might encounter these terms:

* Lowland plains: This emphasizes the flat and low elevation of coastal plains.

* Littoral plains: This refers to the area adjacent to the coast.

* Tidewater plains: This is specific to areas where the influence of tides is significant.

* Alluvial plains: This applies to coastal plains formed by deposition of sediment from rivers.

* Delta plains: This describes plains formed at the mouth of a river.

It's important to understand the context and specific features of the coastal plain when choosing an alternative name.