pupil vs passer

pupil and passer both are nouns.

Word	Noun	Adjective	Verb	Adverb
pupil	Yes	No	No	No
passer	Yes	No	No	No

As nouns, passer is a hyponym of pupil; that is, passer is a word with a more specific, narrower meaning than pupil:

pupil (noun)	passer (noun)
the contractile aperture in the center of the iris of the eye; resembles a large black dot	(football) a ball carrier who tries to gain ground by throwing a forward pass
a learner who is enrolled in an educational institution	a person who passes by casually or by chance
a young person attending school (up through senior high school)	a student who passes an examination
	a person who passes as a member of a different ethnic or racial group