fancy woman vs doxy

fancy woman and doxy both are nouns.

Word	Noun	Adjective	Verb	Adverb
fancy woman	Yes	No	No	No
doxy	Yes	No	No	No

As nouns, doxy is a hyponym of fancy woman; that is, doxy is a word with a more specific, narrower meaning than fancy woman:

fancy woman: an adulterous woman; a woman who has an ongoing extramarital sexual relationship with a man
doxy: a woman who cohabits with an important man

Other hyponyms of fancy woman include concubine, courtesan, paramour.

fancy woman (noun)	doxy (noun)
an adulterous woman; a woman who has an ongoing extramarital sexual relationship with a man	a woman who cohabits with an important man
a woman who engages in sexual intercourse for money