collegian vs college boy

collegian and college boy both are nouns.

Word	Noun	Adjective	Verb	Adverb
collegian	Yes	No	No	No
college boy	Yes	No	No	No

As nouns, collegian and college boy are synonyms defined as:

collegian and college boy: a student (or former student) at a college or university

Other synonyms of collegian include college man.

collegian (noun)	college boy (noun)
a student (or former student) at a college or university	a student (or former student) at a college or university