Source : Webster's Revised Unabridged Dictionary (1913)

Passover \Pass"o`ver\, n. [Pass + over. See Pasch.] (Jewish
   Antiq.)
   (a) A feast of the Jews, instituted to commemorate the
       sparing of the Hebrews in Egypt, when God, smiting the
       firstborn of the Egyptians, passed over the houses of the
       Israelites which were marked with the blood of a lamb.
   (b) The sacrifice offered at the feast of the passover; the
       paschal lamb. --Ex. xii.

Source : WordNet®

Passover
     n : (Judaism) a Jewish festival (traditionally 8 days)
         celebrating the exodus of the Israelites from Egypt [syn:
          {Pesach}, {Pesah}, {Feast of the Unleavened Bread}]