The Collaborative International Dictionary of English v.0.48:

Heinous \Hei"nous\ (h[=a]"n[u^]s), a. [OF. ha["i]nos hateful, F.
   haineux, fr. OF. ha["i]ne hate, F. haine, fr. ha["i]r to
   hate; of German origin. See Hate.]
   Hateful; hatefully bad; flagrant; odious; atrocious; giving
   great offense; -- applied to deeds or to character.
   [1913 Webster]

         It were most heinous and accursed sacrilege. --Hooker.
   [1913 Webster]

         How heinous had the fact been, how deserving
         Contempt!                                --Milton.

   Syn: Monstrous; flagrant; flagitious; atrocious. --
        Hei"nous*ly, adv. -- Hei"nous*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

heinous
    adj 1: extremely wicked, deeply criminal; "a flagitious crime";
           "heinous accusations" [syn: flagitious, heinous]