panty vs step-in

panty and step-in both are nouns.

Word	Noun	Adjective	Verb	Adverb
panty	Yes	No	No	No
step-in	Yes	No	No	No

As nouns, panty and step-in are synonyms defined as:

Other synonyms of panty include pantie, scanty.

panty (noun)	step-in (noun)
short underpants for women or children	short underpants for women or children