lu·​na·​tic | \ ˈlü-nə-ˌtik How to pronounce lunatic (audio) \

Definition of lunatic

1 dated
a : affected with a severely disordered state of mind : insane
b : designed for the care of mentally ill people a lunatic asylum
2 : wildly foolish a lunatic idea lunatic behavior

Keep scrolling for more

Other Words from lunatic

lunatic noun

Synonyms & Antonyms for lunatic



Visit the Thesaurus for More 

Examples of lunatic in a Sentence

He hatched a lunatic plot to overthrow the government. another of his lunatic ideas
Recent Examples on the Web During his stay in Buganda as the guest of its lunatic ruler, Mutesa, Speke witnessed frequent executions and indiscriminate terror. Maxwell Carter, WSJ, 1 Oct. 2021 And your lunatic City Council has no clue as to why crime is rising through the roof? Star Tribune, 26 June 2021 Of course, he was most bemused about the attempt to find evidence of bamboo fibers on the ballots, part of a lunatic right-wing conspiracy theory involving ballots sent from Asia. Bill Goodykoontz, The Arizona Republic, 7 May 2021 It’s another to connect that to a belief in something that appears obviously lunatic like QAnon. David Marchesephoto Illustration By Bráulio Amado, New York Times, 9 Apr. 2021 In fact, all of the outfits are stellar, from Lawrence as some kind of camp voodoo doll to Ellie Diamond, who looks like a lunatic Snow White. Brian Moylan, Vulture, 12 Mar. 2021 Bruno fulfills his end of the deal, but Guy, the other man, never took the pact seriously and refuses to cooperate, sending Bruno into a downward spiral of lunatic frenzy. Terry Teachout, WSJ, 24 Feb. 2021 Few people would stand for a system in which users can be punished for the lunatic interpretations of their followers. Gilad Edelman, Wired, 8 Jan. 2021 Strong absolutely nailed Carone’s appearance, complete with slurred and mispronounced words and lunatic claims and accusations. Bill Goodykoontz, The Arizona Republic, 7 Dec. 2020

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

See More

First Known Use of lunatic

14th century, in the meaning defined at sense 1a

History and Etymology for lunatic

Middle English lunatik, from Anglo-French or Late Latin; Anglo-French lunatic, from Late Latin lunaticus, from Latin luna; from the belief that lunacy fluctuated with the phases of the moon

Keep scrolling for more

Learn More About lunatic

Time Traveler for lunatic

Time Traveler

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

See more words from the same century

Dictionary Entries Near lunatic




See More Nearby Entries 

Statistics for lunatic

Last Updated

8 Oct 2021

Cite this Entry

“Lunatic.” Dictionary, Merriam-Webster, Accessed 27 Oct. 2021.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

Keep scrolling for more

More Definitions for lunatic



English Language Learners Definition of lunatic

: designed for insane people
: not sane
: wildly foolish


lu·​na·​tic | \ ˈlü-nə-ˌtik How to pronounce lunatic (audio) \

Kids Definition of lunatic

 (Entry 1 of 2)



Kids Definition of lunatic (Entry 2 of 2)

1 : an insane person
2 : a person who behaves very foolishly That lunatic went through a red light.


lu·​na·​tic | \ ˈlü-nə-ˌtik How to pronounce lunatic (audio) \

Medical Definition of lunatic

dated, now offensive : an individual marked by a severely disordered state of mind

Keep scrolling for more


lu·​na·​tic | \ ˈlü-nə-tik \

Legal Definition of lunatic

: an insane person used especially formerly

Other Words from lunatic

lunatic adjective

More from Merriam-Webster on lunatic

Nglish: Translation of lunatic for Spanish Speakers

Britannica English: Translation of lunatic for Arabic Speakers


Test Your Vocabulary

Difficult Spelling Words Quiz

  • alphabet pasta spelling help
  • Which is the correct spelling?
Spell It

Can you spell these 10 commonly misspelled words?

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!