Definition of lunatic in English:

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Pronunciation: /ˈlo͞onəˌtik/


1A mentally ill person (not in technical use).
Example sentences
  • She continued to gape at him as if he was a runaway lunatic from a nearby mental asylum.
  • The gaol was also used for a number of years to house the mentally insane, as lunatics had to be restrained and kept out of sight.
  • Initially, he's told he's too old and then parcelled off into the Halberdiers, a regiment almost entirely comprised of oddballs, lunatics, misfits and sociopaths.
1.1An extremely foolish or eccentric person: this lunatic just accelerated out of the side of the road
More example sentences
  • Those of you who are not my best friend Julie, and therefore not lunatics and hardcore math geeks, may not know that today is Pi Day.
  • He has observed that all the other drivers on the road fall into one of two categories: idiots or lunatics.
  • He had known it, the rest of his friends were raving lunatics.
maniac, madman, madwoman, imbecile, psychopath, psychotic;
fool, idiot;
informal loony, nut, nutcase, nutjob, head case, psycho, moron, screwball, crackpot, fruitcake, fruit loop, loon


1Mentally ill (not in technical use).
Example sentences
  • Do you remember that one episode of X-Files with that crazed lunatic writer who was in love with Scully?
  • The frustration is so great that the black character believes that he might wind up in a lunatic cell, driven crazy by the insane demands.
  • I said I found him, not that he was some insane lunatic murderer trying to kill me!
1.1Extremely foolish, eccentric, or absurd: he would be asked to acquiesce in some lunatic scheme
More example sentences
  • What happens if you break all the rules and throw your reputation behind a lunatic scheme to let people hear world-class classical music for the price of a couple of pints?
  • They will presumably lead to some retraction of the lunatic version of markets that have been imposed by extreme reactionaries in recent years.
  • A small smile touched her lips, her eyes alight with a lunatic fire.


Middle English: from Old French lunatique, from late Latin lunaticus, from Latin luna 'moon' (from the belief that changes of the moon caused intermittent insanity).

  • loon from [late 19th century]:

    This word for ‘a silly person’ comes from the North American loon (mid 17th century), a large water bird also known as a diver. It gets its name from its distinctive cry. The sense silly is from the bird's actions when escaping from danger; perhaps influenced by loony, a mid 19th-century abbreviation of lunatic (Middle English) from Latin luna ‘moon. In the past people thought that the phases of the moon could affect people.

For editors and proofreaders

Syllabification: lu·na·tic

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