gay woman vs dyke

gay woman and dyke both are nouns.

Word	Noun	Adjective	Verb	Adverb
gay woman	Yes	No	No	No
dyke	Yes	No	Yes	No

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

Other hyponyms of gay woman include butch, dike.

gay woman (noun)	dyke (noun)
a female homosexual	a barrier constructed to contain the flow of water or to keep out the sea
	(slang) offensive term for a lesbian who is noticeably masculine

gay woman (verb)	dyke (verb)
	enclose with a dike