[ 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).

Origin of lunatic

1250–1300; Middle English lunatik, from Old French lunatique, from Late Latin lūnāticus “moonstruck.” See Luna, -tic


lu·nat·i·cal·ly, adverbhalf-lu·na·tic, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

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 forms of lunatic

lunatically, 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