club sandwich vs three-decker

club sandwich and three-decker both are nouns.

Word	Noun	Adjective	Verb	Adverb
club sandwich	Yes	No	No	No
three-decker	Yes	No	No	No

As nouns, club sandwich and three-decker are synonyms defined as:

club sandwich and three-decker: made with three slices of usually toasted bread

Other synonyms of club sandwich include triple-decker.

club sandwich (noun)	three-decker (noun)
made with three slices of usually toasted bread	a warship carrying guns on three decks
	any ship having three decks
	made with three slices of usually toasted bread