college man vs collegian

college man and collegian both are nouns.

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

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

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

Other synonyms of college man include college boy.

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