triple-decker vs three-decker

triple-decker and three-decker both are nouns.

Word	Noun	Adjective	Verb	Adverb
triple-decker	Yes	No	No	No
three-decker	Yes	No	No	No

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

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

Other synonyms of triple-decker include club sandwich.

triple-decker (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