nightmare

noun

1. 1

   A demon or monster, thought to plague people while they slept and cause a feeling of suffocation and terror during sleep.

2. 2

   Sleep paralysis.

3. 3

   A very bad or frightening dream.

   “I had a nightmare that I tried to run but could neither move nor breathe.”

4. 4

   Any bad, miserable, difficult or terrifying situation or experience that arouses anxiety, terror, agony or great displeasure.

   “Cleaning up after identity theft can be a nightmare of phone calls and letters.”