'Zwieback' definitions:

Definition of 'zwieback'

(from WordNet)
noun
Slice of sweet raised bread baked again until it is brown and hard and crisp [syn: zwieback, rusk, Brussels biscuit, twice-baked bread]

Definition of 'Zwieback'

From: GCIDE
  • Zwieback \Zwie"back`\ (tsv[=e]"b[aum]k`), n. [G., fr. zwie- two, twice (see Twice) + backen to bake.] A kind of biscuit or rusk first baked in a loaf and afterwards cut and toasted. [Webster 1913 Suppl.]