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

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Other Words from nightmare

nightmare adjective
nightmarish \ ˈnīt-​ˌmer-​ish How to pronounce nightmarish (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 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 Now her book describes a ‘nightmare’ of family dysfunction. Washington Post, "1 person dead, 2 wounded in shootings in Arlington County early Saturday," 28 June 2020 Getting dry shampoo to work on dyed black hair is ordinarily a nightmare. Hatti Rex,, "I Tried 5 Viral TikTok Beauty Hacks — & These Are The Results," 25 June 2020 Here’s a common nightmare scenario: The computer system at your doctor’s office is hacked, and somebody has all your medical records. Ge Bai And John (xuefeng) Jiang, WSJ, "How to Prevent Medical Records From Being Hacked," 22 June 2020 The pandemic has created a nightmare scenario for coaches, with players spending the last four months living and training on their own and not under team supervision. Ben Volin,, "Here is what the NFL and NFLPA need to figure out before training camps open," 20 June 2020 For computer scientists who study election software, online-voting programs are a security nightmare. Sue Halpern, The New Yorker, "Why You Can’t Just Vote on Your Phone During the Pandemic," 19 June 2020 Together these two men spent nearly half a century locked up, praying each day to be released from their American nightmare. Tanya A. Christian, Essence, "Two Tulsa Brothers Speak Out After Being Wrongfully Convicted Of Separate Crimes," 19 June 2020 Then, physician and health care policy expert Ezekiel Emanuel joins us to discuss his nightmare scenario: President Trump, desperate for re-election, forces the approval of an ineffective coronavirus vaccine. Rebecca Robbins, STAT, "Listen: The latest on treating Covid-19, vaccine politics, and diversifying genetics," 18 June 2020 The nightmare scenario is a descent into deepening disorder. The Economist, "Time to rediscover statesmanship Three future scenarios for the UN," 20 June 2020

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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Statistics for nightmare

Last Updated

4 Jul 2020

Cite this Entry

“Nightmare.” Dictionary, Merriam-Webster, Accessed 10 Jul. 2020.

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More Definitions for nightmare


How to pronounce nightmare (audio)

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

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