There isn't one single perfect synonym for "cosmological" as it encompasses a broad concept. However, depending on the context, some suitable alternatives could be:

* Cosmic: This is a more general term that refers to the universe as a whole.

* Astrophysical: This focuses on the physical properties and processes of celestial objects.

* Cosmophysical: This term combines the aspects of cosmology and physics.

* Universe-related: This is a more straightforward and less formal option.

* Universal: This term emphasizes the scope of the subject.

The best substitute will depend on the specific context of your writing.