annual Jewish feast instituted to commemorate the escape from Egypt, 1530, coined by Tyndale from verbal phrase pass over, to translate Hebrew ha-pesah "Passover," from pesah (see paschal), in reference to the Lord "passing over" the houses of the Israelites in Egypt when he killed the first-born of the Egyptians (Exodus xii). By extension including the following seven days during which the Israelites were permitted to eat only unleavened bread.

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Definitions of Passover from WordNet

Passover (n.)
(Judaism) a Jewish festival (traditionally 8 days from Nissan 15) celebrating the exodus of the Israelites from Egypt;
Synonyms: Pesach / Pesah / Feast of the Unleavened Bread