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]

WordNet (r) 3.0 (2006):

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