from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Suffering from lunacy; insane.
  • adj. Of or for the insane.
  • adj. Wildly or giddily foolish: a lunatic decision.
  • adj. Characterized by lunacy or eccentricity.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. An insane person.
  • adj. crazed, mad, insane, demented

from the GNU version of the Collaborative International Dictionary of English

  • adj. Affected by lunacy; insane; mad; crazy; demented.
  • adj. Of or pertaining to, or suitable for, an insane person; evincing lunacy
  • n. A person affected by lunacy; an insane person, esp. one who has lucid intervals; a madman; a person of unsound mind.

from The Century Dictionary and Cyclopedia

  • Moonstruck; affected by lunacy; periodically insane, with lucid intervals; crazy.
  • Indicating lunacy; in the nature of lunacy.
  • Of or like the moon.
  • n. A person affected with lunacy; specifically, an insane person who has lucid intervals, or one whose unsoundness of mind is acquired, not congenital, as distinguished from an idiot.
  • n. More generally (and in law), any person of unsound mind. See further under lunacy and insanity.
  • n. Synonyms See insanity.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adj. insane and believed to be affected by the phases of the moon
  • n. a reckless impetuous irresponsible person
  • n. an insane person


from The American Heritage® Dictionary of the English Language, 4th Edition

Middle English lunatik, from Old French lunatique, from Latin lūnāticus, from lūna, moon; see leuk- in Indo-European roots.

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Old French lunatique, from Late Latin lunaticus ("moonstruck"), derived from Latin luna ("moon").


  • _Another lunatic_, was the thought that flashed through my mind; another lunatic, the slave of a single idea.

    The Mutiny of the Elsinore

  • Then there is the reference to the moon the term lunatic derives from luna, the Latin word for moon.


  • Vague recollections of Edgar Allan Poe and the works of Charles Reade had surrounded the term lunatic asylum with an atmosphere of feather beds and brutality; the word lunatic conjured up in his mind the idea of a man obviously insane.

    The Man Who Lost Himself

  • I think being described as a lunatic is worthy of my wall of compliments

    Total Bollocks

  • Ron Paul, the one the media and rabid neocons have called a lunatic, is the only sensible candidate in this race. michael

    Paul set to hold separate rally during Republican convention

  • To forfeit liberties because of the lone act of a lunatic is an especially crude response to a simple, if immense, crime.


  • As a Viet Nam vet, I am outraged that this lunatic is allowed to smear veterans and other patriotic americans under your auspices.

    Think Progress » Coulter on Murtha: He Longs “To See U.S. Troops Shot, Humiliated”

  • I smile as I say the word lunatic, hoping to cushion the remark.

    Water Witches

  • Scotland's first minister, Alex Salmond, who is facing a difficult election next month, blamed the violence narrowly on what he called a "lunatic element," but Devine, the historian, sees a more sinister threat.

    NYT > Global Home

  • That's the religious philosophical basis for what I call the lunatic fringe.

    Planet Atheism


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  • A Brief Biography of Joseph Priestly gives insight into lunatic: "While in Birmingham, Joseph Priestley became a member of the Lunar Society. This was an informal group that met monthly when the moon was full so that there would be light to drive home by. Naturally they were called, and called themselves,lunatics. The members were successful manufacturers and professional men who shared an interest in stimulating discussions on philosophy and science and almost any subject that was interesting. The participants included James Watt, Matthew Boulton, Erasmus Darwin, and others." From A Brief Biography of Joseph Priestley, Prepared by members and friends of the Unitiarian Universalist Congregation of the Susquehanna Valley (UUCSV), Northumberland, Pennsylvania (

    March 19, 2012

  • . . . I perceived my entire skin as that of a leopard painted by a meticulous lunatic from a broken home.

    --Vladimir Nabokov, 1974, Look at the Harlequins! p. 243

    June 13, 2009