What is another word for predicate nominative?

There isn't really a single perfect synonym for "predicate nominative," but here are some alternatives depending on the context:

More formal:

* Subject complement

* Nominal predicate

* Predicative nominative

More informal:

* Complement of the subject

* Renaming phrase

* Defining word/phrase

The best option will depend on the specific situation and the level of formality desired.