nightmare

noun

1. a terrifying dream in which the dreamer experiences feelings of helplessness, extreme anxiety, sorrow, etc.
2. a condition, thought, or experience suggestive of a nightmare: the nightmare of his years in prison.
3. (formerly) a monster or evil spirit believed to oppress persons during sleep.

noun

1. a terrifying or deeply distressing dream
2. 1. an event or condition resembling a terrifying dreamthe nightmare of shipwreck
   2. (as modifier)a nightmare drive
3. a thing that is feared
4. (formerly) an evil spirit supposed to harass or suffocate sleeping people

n.

late 13c., “an evil female spirit afflicting sleepers with a feeling of suffocation,” compounded from night + mare (3) “goblin that causes nightmares, incubus.” Meaning shifted mid-16c. from the incubus to the suffocating sensation it causes. Sense of “any bad dream” first recorded 1829; that of “very distressing experience” is from 1831. Cognate with Middle Dutch nachtmare, German Nachtmahr.

n.

1. A dream arousing feelings of intense fear, horror, and distress.
2. An event or experience that is intensely distressing.