noun night·mare \ ˈnīt-ˌmer \
|Updated on: 7 Jul 2018

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




play \ˈnīt-ˌmer-ish\ adjective



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Examples of nightmare in a Sentence

  1. Mommy, I had a really scary nightmare.

  2. The party was a complete nightmare.

Recent Examples of nightmare from the Web

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.

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.

Origin and Etymology of nightmare

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

NIGHTMARE Defined for English Language Learners


Definition of nightmare for English Language Learners

  • : a dream that frightens a sleeping person : a very bad dream

  • : a very bad or frightening experience or situation

NIGHTMARE Defined for Kids


noun night·mare \ ˈnīt-ˌmer \

Definition of nightmare for Students

1 : a frightening dream
2 : a horrible experience


\ˈnīt-ˌmer-ish\ adjective

History for nightmare

The -mare in nightmare comes from an Old English word for a kind of evil spirit. Such spirits were believed to bother people who were sleeping.

Medical Dictionary


noun night·mare \ ˈnīt-ˌma(ə)r, -ˌme(ə)r \

medical Definition of nightmare

: a frightening or distressing dream that usually awakens the sleeper

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