There isn't a single phrase that perfectly encompasses the meaning of "natural geological protuberance". However, depending on the context, some suitable alternatives could be:

* Landform: This is a general term for any natural feature on the Earth's surface.

* Geological formation: This emphasizes the process of its creation.

* Natural elevation: This focuses on the height of the protrusion.

* Rock formation: This specifically refers to a formation made of rock.

* Outcrop: This refers to a part of a rock formation that is exposed on the surface.

* Hill, ridge, mountain: These are specific types of geological protuberances.

Ultimately, the best phrase to use depends on the specific context and the level of detail you want to convey.