fortune teller vs sibyl

fortune teller and sibyl both are nouns.

Word	Noun	Adjective	Verb	Adverb
fortune teller	Yes	No	No	No
sibyl	Yes	No	No	No

As nouns, sibyl is a hyponym of fortune teller; that is, sibyl is a word with a more specific, narrower meaning than fortune teller:

Other hyponyms of fortune teller include chiromancer, palmist, palmister.

fortune teller (noun)	sibyl (noun)
a person who foretells your personal future	(ancient Rome) a woman who was regarded as an oracle or prophet
	a woman who tells fortunes