nightmare

noun

night·​mare ˈnīt-ˌmer 

1

: an evil spirit formerly thought to oppress people during sleep

2

: a frightening dream that usually awakens the sleeper

3

: something (such as an experience, situation, or object) having the monstrous character of a nightmare or producing a feeling of anxiety or terror

nightmare adjective

nightmarish

ˈnīt-ˌmer-ish 

adjective

nightmarishly adverb

Did you know?

Looking at nightmare, you might guess that it is a compound formed from night and mare. If so, your guess is correct. But while the night in nightmare makes sense, the mare part is less obvious. Most English speakers know mare as a word for a female horse or similar equine animal, but the mare of nightmare is a different word, an obsolete one referring to an evil spirit that was once thought to produce feelings of suffocation in people while they slept. By the 14th century the mare was also known as nightmare, and by the late 16th century nightmare was also being applied to the feelings of distress caused by the spirit, and then to frightening or unpleasant dreams.

Synonyms

• agony
• Gehenna
• hell
• horror
• misery
• murder
• torment
• torture

Examples of nightmare in a Sentence

Mommy, I had a really scary nightmare.

The party was a complete nightmare.

Recent Examples on the Web

That would be a double-feature nightmare for Chargers fans. —Gary Klein, Los Angeles Times, 12 Sep. 2023

With a 6-foot-4, big-bodied frame, Fairweather presents as a mismatch nightmare for opposing defenses. —Ainslie Lee | [e-mail], al, 10 Sep. 2023

Black artists with mainstream aspirations in the United States indeed always come up against this nightmare scenario, rife with ignorance, projection, guilt and a dissatisfying seesaw of overhype and chronic underestimation. —Lovia Gyarkye, The Hollywood Reporter, 9 Sep. 2023

Enquirer With his versatility, Highlands senior quarterback Brody Benke can be an absolute nightmare for defenses. —Evan Merrill, The Enquirer, 9 Sep. 2023

All new cars today are privacy nightmares on wheels that collect huge amounts of personal information. —Peter Weber, The Week, 9 Sep. 2023

Its early, comparatively skillful handling of information — interlacing storylines from different timelines as well as dreams, legends and nightmares — achieved interesting resonances without sacrificing clarity. —Lili Loofbourow, Washington Post, 7 Sep. 2023

The only problem is the terrifying red-eyed, midnight black horned demon crawling (and rapping) on her ceiling, illuminated by a snowy TV screen in an homage to another freaky suburban nightmare classic, Poltergeist. —Gil Kaufman, Billboard, 1 Sep. 2023

So there are many reasons to keep your feet dry, especially during colder months when the combination of frigid air and moisture is a nightmare. —Joel Balsam, Travel + Leisure, 29 Aug. 2023

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Word History

Etymology

Middle English nyghte mare, from nyghte night entry 1 + mare mare entry 3

First Known Use

14th century, in the meaning defined at sense 1

Phrases Containing nightmare

• worst nightmare

• worst nightmare

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Kids Definition

nightmare

noun

night·​mare ˈnīt-ˌma(ə)r 

-ˌme(ə)r

1

: a frightening dream

2

: a frightening or horrible experience

nightmarish

-ish 

adjective

Etymology

Middle English nightmare "evil spirit thought to haunt people during sleep," from night "night" and mare "spirit," from Old English mare "evil spirit haunting people in sleep"

Word Origin

In the Middle Ages many people believed in a type of evil spirit that was said to haunt people while they slept. Such a demon was known in Old English as a mare. Because it was believed to come in the night, it later became known in Middle English as a nightmare. It was not until the 16th century that the word nightmare came to mean "a frightening dream." This meaning probably came from the belief that such dreams were caused by evil spirits.

Medical Definition

nightmare

noun

night·​mare ˈnīt-ˌma(ə)r, -ˌme(ə)r 

: a frightening or distressing dream that usually awakens the sleeper