underskirt vs crinoline

underskirt and crinoline both are nouns.

Word	Noun	Adjective	Verb	Adverb
underskirt	Yes	No	No	No
crinoline	Yes	No	No	No

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

underskirt (noun)	crinoline (noun)
undergarment worn under a skirt	a stiff coarse fabric used to stiffen hats or clothing
	a full stiff petticoat made of crinoline fabric
	a skirt stiffened with hoops