Horror, n.
Etymology: [Formerly written horrour.]
Etym: [L. horror, fr. horrere to bristle, to shiver, to tremble with cold or dread, to be dreadful or terrible; cf. Skr. h to bristle.]
1. A bristling up; a rising into roughness; tumultuous movement. [Archaic] Such fresh horror as you see driven through the wrinkled waves. Chapman.
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.
3. A painful emotion of fear, dread, and abhorrence; a shuddering with terror and detestation; the feeling inspired by something frightful and shocking. How could this, in the sight of heaven, without horrors of conscience be uttered Milton.
1 more senses
4. That which excites horror or dread, or is horrible; gloom; dreariness. Breathes a browner horror on the woods. Pope. The horrors, delirium tremens. [Colloq.]
Shades of meaning
Fernald has no entry of its own for horror; he lists it under abomination, fear.
Where he writes about it:
Horror (etymologically a shivering or shuddering) denotes a shuddering fear accompanied with abhorrence or such a shock to the feelings and sensibilities as may exist without fear, as when one suddenly encounters some ghastly spectacle; we say of a desperate but fettered criminal, "I looked upon him with horror." Where horror includes fear, it is fear mingled with abhorrence. (See abhor.) Affright, fright, and terror are always sudden, and in actual presence of that which is terrible. — from fear