What is a person who no longer student called?

There isn't one single word to describe someone who is no longer a student. The best term depends on the context:

* Graduate: This is suitable if they completed their studies.

* Alumnus/Alumna (Alumni for plural): This refers to a former student of a specific school or university.

* Professional: This is appropriate if they are now employed in a professional capacity.

* Adult: This is a general term, but may be suitable in some contexts.

* Working adult: This clarifies their employment status.

The most accurate term will depend on what you want to emphasize about the person.