The Collaborative International Dictionary of English v.0.48:

Horrify \Hor"ri*fy\, v. t. [imp. & p. p. Horrified; p. pr. &
   vb. n. Horrifying.] [L. horrificare. See Horrific.]
   To cause to feel horror; to strike or impress with horror;
   as, the sight horrified the beholders. --E. Irving.
   [1913 Webster]

WordNet (r) 3.0 (2006):

horrify
    v 1: fill with apprehension or alarm; cause to be unpleasantly
         surprised; "I was horrified at the thought of being late
         for my interview"; "The news of the executions horrified
         us" [syn: dismay, alarm, appal, appall, horrify]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "horrify":
   alarm, appall, awe, daunt, disconcert, discountenance, disgust,
   dismay, distress, freeze, frighten, give offense, gross out,
   intimidate, nauseate, offend, outrage, panic, paralyze, petrify,
   put off, repel, revolt, scare, scare stiff, scare to death, shake,
   shock, sicken, startle, strike dumb, strike terror into, stun,
   stupefy, terrify, turn the stomach, upset