collegian vs pupil

collegian and pupil both are nouns.

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

As nouns, pupil is a hypernym of collegian; that is, pupil is a word with a broader meaning than collegian:

Other hypernyms of collegian include educatee, student.

collegian (noun)	pupil (noun)
a student (or former student) at a college or university	the contractile aperture in the center of the iris of the eye; resembles a large black dot
	a learner who is enrolled in an educational institution
	a young person attending school (up through senior high school)