The Collaborative International Dictionary of English v.0.48:

Pasch \Pasch\, Pascha \Pas"cha\, n. [AS. pascha, L. pascha, Gr.
   ?, fr. Heb. pesach, fr. p[=a]sach to pass over: cf. OF.
   pasque, F. p[^a]que. Cf. Paschal, Paas, Paque.]
   The passover; the feast of Easter.
   [1913 Webster]

   Pasch egg. See Easter egg, under Easter.

   Pasch flower. See Pasque flower, under Pasque.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Easter \Eas"ter\ ([=e]s"t[~e]r), n. [AS. e['a]ster, e['a]stran,
   paschal feast, Easter; akin to G. ostern; fr. AS. E['a]stre,
   a goddess of light or spring, in honor of whom a festival was
   celebrated in April; whence this month was called in AS.
   E['a]sterm[=o]na[eth]. From the root of E. east. See East.]
   1. An annual church festival commemorating Christ's
      resurrection, and occurring on Sunday, the second day
      after Good Friday. It corresponds to the pascha or
      passover of the Jews, and most nations still give it this
      name under the various forms of pascha, pasque,
      p[^a]que, or pask.
      [1913 Webster]

   2. The day on which the festival is observed; Easter day.
      [1913 Webster]

   Note: Easter is used either adjectively or as the first
         element of a compound; as, Easter day or Easter-day,
         Easter Sunday, Easter week, Easter gifts, Easter eggs.
         [1913 Webster]

               Sundays by thee more glorious break,
               An Easter day in every week.       --Keble.
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   Note: Easter day, on which the rest of the movable feasts
         depend, is always the first Sunday after the fourteenth
         day of the calendar moon which (fourteenth day) falls
         on, or next after, the 21st of March, according to the
         rules laid down for the construction of the calendar;
         so that if the fourteenth day happen on a Sunday,
         Easter day is the Sunday after. --Eng. Cyc.
         [1913 Webster]

   Easter dues (Ch. of Eng.), money due to the clergy at
      Easter, formerly paid in communication of the tithe for
      personal labor and subject to exaction. For Easter dues,
      Easter offerings, voluntary gifts, have been substituted.


   Easter egg.
      (a) A painted or colored egg used as a present at Easter.
      (b) An imitation of an egg, in sugar or some fine
          material, sometimes made to serve as a box for jewelry
          or the like, used as an Easter present.
          [1913 Webster]

WordNet (r) 3.0 (2006):

Pascha
    n 1: the Jewish feast of the Passover [syn: Pasch, Pascha]
    2: the Christian festival of Easter [syn: Pasch, Pascha]