old woman vs beldame

old woman and beldame both are nouns.

Word	Noun	Adjective	Verb	Adverb
old woman	Yes	No	No	No
beldame	Yes	No	No	No

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

Other hyponyms of old woman include beldam, granny, beldam, crone, hag, witch, mother.

old woman (noun)	beldame (noun)
a woman who is old	a woman of advanced age
herb with greyish leaves found along the east coast of North America; used as an ornamental plant	an ugly evil-looking old woman