The Collaborative International Dictionary of English v.0.48:

Horror \Hor"ror\, n. [Formerly written horrour.] [L. horror, fr.
   horrere to bristle, to shiver, to tremble with cold or dread,
   to be dreadful or terrible; cf. Skr. h?sh to bristle.]
   1. A bristling up; a rising into roughness; tumultuous
      movement. [Archaic]
      [1913 Webster]

            Such fresh horror as you see driven through the
            wrinkled waves.                       --Chapman.
      [1913 Webster]

   2. A shaking, shivering, or shuddering, as in the cold fit
      which precedes a fever; in old medical writings, a chill
      of less severity than a rigor, and more marked than an
      algor.
      [1913 Webster]

   3. A painful emotion of fear, dread, and abhorrence; a
      shuddering with terror and detestation; the feeling
      inspired by something frightful and shocking.
      [1913 Webster]

            How could this, in the sight of heaven, without
            horrors of conscience be uttered?     --Milton.
      [1913 Webster]

   4. That which excites horror or dread, or is horrible; gloom;
      dreariness.
      [1913 Webster]

            Breathes a browner horror on the woods. --Pope.
      [1913 Webster]

   The horrors, delirium tremens. [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

horror
    n 1: intense and profound fear
    2: something that inspires dislike; something horrible; "the
       painting that others found so beautiful was a horror to him"
    3: intense aversion [syn: repugnance, repulsion,
       revulsion, horror]