rummage sale vs cut-rate sale

rummage sale and cut-rate sale both are nouns.

Word	Noun	Adjective	Verb	Adverb
rummage sale	Yes	No	No	No
cut-rate sale	Yes	No	No	No

As nouns, cut-rate sale is a hypernym of rummage sale; that is, cut-rate sale is a word with a broader meaning than rummage sale:

rummage sale: a sale of donated articles
cut-rate sale: an occasion (usually brief) for buying at specially reduced prices

Other hypernyms of rummage sale include sale, sales event.

rummage sale (noun)	cut-rate sale (noun)
a sale of donated articles	an occasion (usually brief) for buying at specially reduced prices