garter belt vs undergarment

garter belt and undergarment both are nouns.

Word	Noun	Adjective	Verb	Adverb
garter belt	Yes	No	No	No
undergarment	Yes	No	No	No

As nouns, undergarment is a hypernym of garter belt; that is, undergarment is a word with a broader meaning than garter belt:

garter belt: a wide belt of elastic with straps hanging from it; worn by women to hold up stockings
undergarment: a garment worn under other garments

Other hypernyms of garter belt include unmentionable.

garter belt (noun)	undergarment (noun)
a wide belt of elastic with straps hanging from it; worn by women to hold up stockings	a garment worn under other garments