visiting professor vs professor

visiting professor and professor both are nouns.

Word	Noun	Adjective	Verb	Adverb
visiting professor	Yes	No	No	No
professor	Yes	No	No	No

As nouns, professor is a hypernym of visiting professor; that is, professor is a word with a broader meaning than visiting professor:

visiting professor: a professor visiting another college or university to teach for a limited time
professor: someone who is a member of the faculty at a college or university

Other hypernyms of visiting professor include prof.

visiting professor (noun)	professor (noun)
a professor visiting another college or university to teach for a limited time	someone who is a member of the faculty at a college or university