back talk vs retort

back talk and retort both are nouns.

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

As nouns, retort is a hypernym of back talk; that is, retort is a word with a broader meaning than back talk:

back talk: an impudent or insolent rejoinder
retort: a quick reply to a question or remark (especially a witty or critical one)

Other hypernyms of back talk include comeback, counter, rejoinder, replication, return, riposte.

back talk (noun)	retort (noun)
an impudent or insolent rejoinder	a vessel where substances are distilled or decomposed by heat
	a quick reply to a question or remark (especially a witty or critical one)

back talk (verb)	retort (verb)
	answer back