back talk vs sass

back talk and sass both are nouns.

Word	Noun	Adjective	Verb	Adverb
back talk	Yes	No	No	No
sass	Yes	No	Yes	No

As nouns, back talk and sass are synonyms defined as:

Other synonyms of back talk include backtalk, lip, mouth, sassing.

back talk (noun)	sass (noun)
an impudent or insolent rejoinder	an impudent or insolent rejoinder

back talk (verb)	sass (verb)
	answer back in an impudent or insolent manner