You can refer to an account of a very unpleasant experience or event as a horror story. a horror story about lost luggage while flying
You can refer to extremely unpleasant or frightening experiences as horrors. Can you possibly imagine all the horrors we have undergone since I last wrote you?
Horror is a feeling of great shock, fear, and worry caused by something extremely unpleasant. As I watched in horror the boat began to power away from me. = terror
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