zwieback n slice of sweet raised bread baked again until it is brown and hard and crisp Usage(s) It also makes bread, dog biscuits, Shredded Wheat, gingerbread goodies, peanut butter, zwieback, macaroni, pretzels. He likes baked potatoes, butter, spinach, zwieback, watches that have a loud tick. Prudence Penny, the New York Mirror's cooking columnist, was teaching readers how to make rum pie with zwieback crust. Synonym(s) rusk Brussels biscuit twice-baked bread