lip vs back talk

lip and back talk both are nouns.

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

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

Other synonyms of lip include backtalk, mouth, sass, sassing.

lip (noun)	back talk (noun)
either the outer margin or the inner margin of the aperture of a gastropod's shell	an impudent or insolent rejoinder
the top edge of a vessel or other container
either of two fleshy folds of tissue that surround the mouth and play a role in speaking
an impudent or insolent rejoinder
(botany) either of the two parts of a bilabiate corolla or calyx