night·​mare | \ ˈnīt-ˌmer How to pronounce nightmare (audio) \

Definition of nightmare

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

Other Words from nightmare

nightmare adjective
nightmarish \ ˈnīt-​ˌmer-​ish How to pronounce nightmare (audio) \ adjective
nightmarishly adverb

Synonyms & Antonyms for nightmare



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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.

Examples of nightmare in a Sentence

Mommy, I had a really scary nightmare. The party was a complete nightmare.
Recent Examples on the Web Because phones today have all sorts of sensitive personal and financial information, a stolen or lost iPhone can be nothing short of a harrowing nightmare. Yoni Heisler, BGR, 15 Jan. 2022 Loosely based on a podcast of the same name, this mind-bending puzzle pits sanity against reality where the pursuit of lucidity is both a nightmare and a thrill. Los Angeles Times, 14 Jan. 2022 America’s dream couple, or nightmare couple depending on your feelings for Megan Fox and Machine Gun Kelly, is engaged. Troy L. Smith, cleveland, 13 Jan. 2022 Living with Phil Spector was a waking nightmare for Ronnie, who described years of psychological torture in her 1990 memoir, Be My Baby. Lester Fabian Brathwaite,, 13 Jan. 2022 For his unvaccinated sister, a nightmare began to unfold. Carolyn Barber, Scientific American, 12 Jan. 2022 The idea to install a marble floor in the kitchen by himself went from dream to nightmare. Dean Irvine, CNN, 11 Jan. 2022 Residents at the Twin Parks North West tower in the Bronx awoke to children and chores — and then the morning twisted in an instant into a blackening nightmare. New York Times, 9 Jan. 2022 Santos’ field goal in the final seconds lifted the Bears to a 16-14 victory over the Lions that snapped a five-game losing streak and ended a nightmare of a week. Colleen Kane,, 9 Jan. 2022

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'nightmare.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of nightmare

14th century, in the meaning defined at sense 1

History and Etymology for nightmare

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

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Time Traveler for nightmare

Time Traveler

The first known use of nightmare was in the 14th century

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Dictionary Entries Near nightmare



night monkey

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Last Updated

18 Jan 2022

Cite this Entry

“Nightmare.” Dictionary, Merriam-Webster, Accessed 29 Jan. 2022.

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More Definitions for nightmare



English Language Learners Definition of nightmare

: a dream that frightens a sleeping person : a very bad dream
: a very bad or frightening experience or situation


night·​mare | \ ˈnīt-ˌmer How to pronounce nightmare (audio) \

Kids Definition of nightmare

1 : a frightening dream
2 : a horrible experience

Other Words from nightmare

nightmarish \ ˈnīt-​ˌmer-​ish \ adjective


night·​mare | \ ˈnīt-ˌma(ə)r, -ˌme(ə)r How to pronounce nightmare (audio) \

Medical Definition of nightmare

: a frightening or distressing dream that usually awakens the sleeper

More from Merriam-Webster on nightmare

Nglish: Translation of nightmare for Spanish Speakers

Britannica English: Translation of nightmare for Arabic Speakers Encyclopedia article about nightmare


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