[ loo-nuh-tik ]
/ ˈlu nə tɪk /


(no longer in technical use; now considered offensive) an insane person.
a person whose actions and manner are marked by extreme eccentricity or recklessness.
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.

adjective Also lu·nat·i·cal [loo-nat-i-kuh l] /luˈnæt ɪ kəl/ (for defs 4, 5, 7).

Nearby words

  1. lunarian,
  2. lunarscape,
  3. lunate,
  4. lunate bone,
  5. lunately,
  6. lunatic asylum,
  7. lunatic fringe,
  8. lunatical,
  9. lunation,
  10. lunch

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 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for lunatic

British Dictionary definitions for lunatic


/ (ˈluːnətɪk) /

adjective Also (rarely): lunatical (luːˈnætɪkəl)

an archaic word for insane
foolish; eccentric; crazy


a person who is insane
Derived Formslunatically, adverb

Word Origin for lunatic

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
Online Etymology Dictionary, © 2010 Douglas Harper