zwie·back (sw??b?k?, -bäk?, sw??-, zw??-, zw??-)n. A usually sweetened bread first baked as a loaf and later cut into slices and toasted.[German : zwie-, twice (from Middle High German zwi-, from Old High German; see dwo- in Indo-European roots) + backen, to bake (from Middle High German, from Old High German bahhan, backan).]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.zwieback (?zwa??bæk; ?zwi?-; German ?tsvi?bak) n (Cookery) a small type of rusk, which has been baked first as a loaf, then sliced and toasted, usually bought ready-made[German: twice-baked]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014zwie?back (?zwa??bæk, -?b?k, ?zwi-, ?swa?-, ?swi-) n. an egg bread, often sweetened, that is baked, sliced and dried, then baked again until crisp. [1890?95, Amer.;