dancer vs taxi dancer

dancer and taxi dancer both are nouns.

Word	Noun	Adjective	Verb	Adverb
dancer	Yes	No	No	No
taxi dancer	Yes	No	No	No

As nouns, taxi dancer is a hyponym of dancer; that is, taxi dancer is a word with a more specific, narrower meaning than dancer:

dancer: a performer who dances professionally
taxi dancer: a woman employed to dance with patrons who pay a fee for each dance

dancer (noun)	taxi dancer (noun)
a performer who dances professionally	a woman employed to dance with patrons who pay a fee for each dance
a person who participates in a social gathering arranged for dancing (as a ball)