zwieback vs rusk

zwieback and rusk both are nouns.

Word	Noun	Adjective	Verb	Adverb
zwieback	Yes	No	No	No
rusk	Yes	No	No	No

As nouns, zwieback and rusk are synonyms defined as:

zwieback and rusk: slice of sweet raised bread baked again until it is brown and hard and crisp

Other synonyms of zwieback include Brussels biscuit, twice-baked bread.

zwieback (noun)	rusk (noun)
slice of sweet raised bread baked again until it is brown and hard and crisp	slice of sweet raised bread baked again until it is brown and hard and crisp