first team vs varsity

first team and varsity both are nouns.

Word	Noun	Adjective	Verb	Adverb
first team	Yes	No	No	No
varsity	Yes	No	No	No

As nouns, first team and varsity are synonyms defined as:

first team (noun)	varsity (noun)
a team representing a college or university	a British abbreviation of `university'; usually refers to Oxford University or Cambridge University
	a team representing a college or university