NIGHTMARE

nightmare

(noun) a terrifying or deeply upsetting dream

nightmare, incubus

(noun) a situation resembling a terrifying dream

Source: WordNet® 3.1

Etymology

Noun

nightmare (plural nightmares)

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

(obsolete) Sleep paralysis.

A very bad or frightening dream.

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

Synonyms

• (demon said to torment sleepers): incubus, succubus, night hag

Source: Wiktionary

Night"mare`, n. Etym: [Night + mare incubus. See Mare incubus.]

1. A fiend or incubus formerly supposed to cause trouble in sleep.

2. A condition in sleep usually caused by improper eating or by digestive or nervous troubles, and characterized by a sense of extreme uneasiness or discomfort (as of weight on the chest or stomach, impossibility of motion or speech, etc.), or by frightful or oppressive dreams, from which one wakes after extreme anxiety, in a troubled state of mind; incubus. Dunglison.

3. Hence, any overwhelming, oppressive, or stupefying influence.

Source: Webster’s Unabridged Dictionary 1913 Edition