undergrad vs undergraduate

undergrad and undergraduate both are nouns.

Word	Noun	Adjective	Verb	Adverb
undergrad	Yes	No	No	No
undergraduate	Yes	No	No	No

As nouns, undergrad and undergraduate are synonyms defined as:

undergrad and undergraduate: a university student who has not yet received a first degree

undergrad (noun)	undergraduate (noun)
a university student who has not yet received a first degree	a university student who has not yet received a first degree