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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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 a 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 The nightmare scenario for Biden (and his party) is the presidency of George W. Bush, who saw his approval rating go as low as 25% in the midst of the global financial crisis in October 2008. Chris Cillizza, CNN, 18 Nov. 2021 The nightmare scenario that public health officials had long warned about began to unfold: The virus started racing through some of the hundreds of displacement camps. Washington Post, 2 Nov. 2021 Rather than the usual nightmare scenario of generals unleashing autonomous killing machines, the concern is that the machines will find the targets and delegate killing to the humans. David Hambling, Forbes, 28 Oct. 2021 That's my nightmare scenario, but that's number one. CBS News, 27 Oct. 2021 Oregon officials say their nightmare scenario unfolded 11 years ago in Seattle. oregonlive, 3 Oct. 2021 That’s because the science thus far tells us that a sporting event, especially indoors, where people are packed inside and yelling, is a nightmare scenario for preventing the spread of COVID. Robert Gehrke, The Salt Lake Tribune, 1 Oct. 2021 That was the nightmare scenario faced by Connie Parke of Aurora, Colorado. Alyssa Marino, USA TODAY, 17 Sep. 2021 That nightmare scenario was avoided, in large part because of an unprecedented response from the federal government that included stimulus checks, small business loans and emergency credit programs. Matt Egan, CNN, 17 Sep. 2021

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

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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

26 Nov 2021

Cite this Entry

“Nightmare.” Dictionary, Merriam-Webster, Accessed 2 Dec. 2021.

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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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