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

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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

Someone who might take our hand, as if taking the hand of an errant toddler, and gently guide us away from the lunatic precipice that the ‘logic’ of profit unguided by the compass of feeling has brought us to. Sydney Bucksbaum,, "Brit Marling responds to The OA cancelation fan hunger strike: 'No one is coming to the rescue'," 24 Aug. 2019 The El Paso massacre, carried out by a white nationalist waging a lunatic war against Hispanic immigration, is being used as a bludgeon against Trump, and immigration restriction more broadly. Rich Lowry, National Review, "Immigration Restriction Is Not Hate," 9 Aug. 2019 The physical comedy requires the cast members to boomerang around the set with lunatic abandon. Charles Mcnulty,, "Review: How funny is ‘The Play That Goes Wrong’? Depends on your appetite for pranks and pratfalls," 12 July 2019 In the gloaming, these white jumpsuits, moving irregularly amid the deep green of the manicured grounds, brought to mind an avant-garde film about a lunatic asylum: the inmates, in their hospital gowns, out for a constitutional. Nick Paumgarten, The New Yorker, "Inside the Cultish Dreamworld of Augusta National," 14 June 2019 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

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

Last Updated

8 Sep 2019

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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



English Language Learners Definition of lunatic

old-fashioned + sometimes offensive : 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

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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

Comments on lunatic

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involving a confidence or trust

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