dancer vs showgirl

dancer and showgirl both are nouns.

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

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

dancer (noun)	showgirl (noun)
a performer who dances professionally	a woman who dances in a chorus line
a person who participates in a social gathering arranged for dancing (as a ball)