matzo, unleavened bread eaten by Jews during the holiday of Passover (Pesaḥ) in commemoration of their Exodus from Egypt. The rapid departure from Egypt did not allow for the fermentation of dough, and thus the use of leavening of any kind is proscribed throughout the week-long holiday.
The Passover ritual requires that Jews eat matzos at least on the first night of the celebration. Among observant Jews it is customary, however, to eat matzos throughout Passover.