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lunatic

[loo-nuh-tik]
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noun
  1. (no longer in technical use; now considered offensive) an insane person.
  2. a person whose actions and manner are marked by extreme eccentricity or recklessness.
  3. a person legally declared to be of unsound mind and who therefore is not held capable or responsible before the law: a former legal term.
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adjective Also lu·nat·i·cal [loo-nat-i-kuh l] /luˈnæt ɪ kəl/ (for defs 4, 5, 7).
  1. (no longer in technical use; now considered offensive) insane.
  2. characteristic or suggestive of lunacy; wildly or recklessly foolish.
  3. Older Use. designated for or used by the insane: a lunatic asylum.
  4. gaily or lightheartedly mad, frivolous, eccentric, etc.: She has a lunatic charm that is quite engaging.
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Origin of lunatic

1250–1300; Middle English lunatik, from Old French lunatique, from Late Latin lūnāticus “moonstruck.” See Luna, -tic
Related formslu·nat·i·cal·ly, adverbhalf-lu·na·tic, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for lunatic

lunatic

adjective Also (rarely): lunatical (luːˈnætɪkəl)
  1. an archaic word for insane
  2. foolish; eccentric; crazy
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noun
  1. a person who is insane
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Derived Formslunatically, adverb

Word Origin

C13 (adj) via Old French from Late Latin lūnāticus crazy, moonstruck, from Latin lūna moon
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for lunatic

adj.

late 13c., "affected with periodic insanity, dependent on the changes of the moon," from Old French lunatique, lunage "insane," or directly from Late Latin lunaticus "moon-struck," from Latin luna "moon" (see Luna). Cf. Old English monseoc "lunatic," literally "moon-sick;" Middle High German lune "humor, temper, mood, whim, fancy" (German Laune), from Latin luna. Cf. also New Testament Greek seleniazomai "be epileptic," from selene "moon." Lunatic fringe (1913) apparently was coined by U.S. politician Theodore Roosevelt.

Then, among the wise and high-minded people who in self-respecting and genuine fashion strive earnestly for peace, there are foolish fanatics always to be found in such a movement and always discrediting it -- the men who form the lunatic fringe in all reform movements. [Theodore Roosevelt, autobiography, 1913].

Earlier it was a term for a type of hairstyle worn over the forehead (1877). Lunatic soup (1933) was Australian slang for "alcoholic drink."

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n.

"lunatic person," late 14c., from lunatic (adj.).

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Online Etymology Dictionary, © 2010 Douglas Harper