lu·​na·​tic | \ ˈlü-nə-ˌtik \

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

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Other Words from lunatic

lunatic noun

Synonyms & Antonyms for lunatic


balmy, barmy [chiefly British], bats, batty, bedlam, bonkers, brainsick, bughouse [slang], certifiable, crackbrained, cracked, crackers, crackpot, cranky [dialect], crazed, crazy, cuckoo, daffy, daft, demented, deranged, fruity [slang], gaga, haywire, insane, kooky (also kookie), loco [slang], loony (also looney), loony tunes (or looney tunes), mad, maniacal (also maniac), mental, meshuga (or meshugge), moonstruck, non compos mentis, nuts, nutty, psycho, psychotic, scatty [chiefly British], screwy, unbalanced, unhinged, unsound, wacko (also whacko), wacky (also whacky), wud [chiefly Scottish]


balanced, compos mentis, sane, sound, uncrazy

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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

Robin Williams had the same thing going for him: a lunatic brilliance that none of his movies ever truly utilized effectively. Soren Andersen, The Seattle Times, "‘The Spy Who Dumped Me’: Kate McKinnon makes familiar action comedy something special," 30 July 2018 Which, according to some lunatic math, saves you two pounds a year. Samantha Leal, Marie Claire, "Blotting Your Pizza with a Napkin Is a Lie," 1 Oct. 2015 The indelible writer, actress, lunatic cabaret star and occasional solo performer Erin Markey comes to the Bushwick Starr with a two-hander, co-starring her friend Emily Davis. Alexis Soloski, New York Times, "11 Plays and Musicals to Go to in N.Y.C. This Weekend," 17 May 2018 Amanda Peet says her house often resembles a lunatic asylum. Jessica Gelt,, "Amanda Peet, playwright: How the actress became the author of the Geffen's upcoming premiere," 13 June 2018 Nick Drnaso's new graphic novel, Sabrina (Drawn & Quarterly), is a subtle, heart-wrenching, multifaceted look at loneliness and loss in our lunatic asylum of a country and an impressive follow-up to his 2016 debut, Beverly. Mark Peters, Chicago Reader, "Nick Drnaso’s second graphic novel, Sabrina, examines the perils of living too long in your own head," 22 May 2018 Only a minute remained of the second leg of this Champions League semifinal, sixty more seconds after three frantic, chaotic, lunatic hours of soccer over two games. Rory Smith, New York Times, "Champions League: Liverpool Ousts Roma in Loss That Doubles as a Triumph," 2 May 2018 The indelible writer, actress, lunatic cabaret star and occasional solo performer Erin Markey comes to the Bushwick Starr with a play for two, co-starring her friend Emily Davis. Alexis Soloski, New York Times, "9 Plays and Musicals to Go to in N.Y.C. This Weekend," 10 May 2018 Argentina’s economy had been battered by the lunatic policies of a succession of populist governments. The Economist, "Argentina’s economic woes," 10 May 2018

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.

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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

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Dictionary Entries near lunatic






lunatic fringe


Statistics for lunatic

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Time Traveler for lunatic

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

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More Definitions for lunatic


lu·​na·​tic | \ ˈlü-nə-ˌtik \

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.



Medical Definition of lunatic

: an individual marked by a severely disordered state of mind


lu·​na·​tic | \ ˈlü-nə-tik\

Legal Definition of lunatic

: an insane person used especially formerly

Other Words from lunatic

lunatic adjective

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More from Merriam-Webster on lunatic

Rhyming Dictionary: Words that rhyme with lunatic

Thesaurus: All synonyms and antonyms for lunatic

Spanish Central: Translation of lunatic

Nglish: Translation of lunatic for Spanish Speakers

Britannica English: Translation of lunatic for Arabic Speakers

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irregularly rounded

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