Definition of "zwieback"

zwieback

noun
countable and uncountable, plural zwiebacks
1. A form of rusk, usually sweetened bread enriched with eggs that is baked and then sliced and toasted until dry and crisp; considered easy to digest and therefore given to the ill and used as a teething food for toddlers.
  Quotations
  She nibbled the zwieback that she always fed off,And when it was gone, she cut the giant's head off.
  Ogden Nash, Adventures Of Isabel