The Collaborative International Dictionary of English v.0.48:

Blasphemy \Blas"phe*my\, n. [L. blasphemia, Gr. ?: cf. OF.
   blasphemie.]
   1. An indignity offered to God in words, writing, or signs;
      impiously irreverent words or signs addressed to, or used
      in reference to, God; speaking evil of God; also, the act
      of claiming the attributes or prerogatives of deity.
      [1913 Webster]

   Note: When used generally in statutes or at common law,
         blasphemy is the use of irreverent words or signs in
         reference to the Supreme Being in such a way as to
         produce scandal or provoke violence.
         [1913 Webster]

   2. Figuratively, of things held in high honor: Calumny;
      abuse; vilification.
      [1913 Webster]

            Punished for his blasphemy against learning.
                                                  --Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

blasphemy
    n 1: blasphemous language (expressing disrespect for God or for
         something sacred)
    2: blasphemous behavior; the act of depriving something of its
       sacred character; "desecration of the Holy Sabbath" [syn:
       profanation, desecration, blasphemy, sacrilege]