The Collaborative International Dictionary of English v.0.48:

Heretical \He*ret"i*cal\, a.
   Containing heresy; of the nature of, or characterized by,
   heresy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

heretical
    adj 1: characterized by departure from accepted beliefs or
           standards [syn: dissident, heretical, heterodox]