taking an entrance exam just for the experience; applying to a school without expecting to pass
Used when someone sits an entrance exam mainly as a trial run, for the experience, or as a symbolic gesture, without a realistic expectation of admission. Often carries a light, self-deprecating tone.
It wasn't my first choice, but I took the exam just for the experience.
He took the University of Tokyo entrance exam without expecting to pass, but surprisingly got accepted.
受験 is the general term for taking an exam. 記念受験 specifically adds the nuance of doing it for the experience or as a symbolic attempt, not as a serious bid for admission.
Compound of 記念 (commemoration, remembrance) and 受験 (taking an exam). The word suggests taking an exam as a kind of memento or experience rather than for practical admission purposes.