SKIP TO CONTENT

lunatic

/ˌlunəˈtɪk/
/ˈlunətɪk/
IPA guide

Other forms: lunatics

A lunatic is someone who is either clinically insane or just acting really crazy. Someone driving too fast and zigging in and out of traffic is driving like a lunatic.

The root of this word is luna, which means moon. That's because lunatic originally meant someone who went crazy with every phase of the moon, kind of like a werewolf. Most people these days don't believe in moon-caused insanity, but we still talk about lunatics, sometimes meaning clinically insane people. More often this is a slang term, used mainly in exaggerations, for anyone who seems wild and out of control.

Definitions of lunatic
  1. noun
    an insane person
    synonyms: madman, maniac
    see moresee less
    types:
    crazy, looney, loony, nutcase, weirdo
    someone deranged and possibly dangerous
    bedlamite
    an archaic term for a lunatic
    pyromaniac
    a person with a mania for setting things on fire
    madwoman
    a woman lunatic
    type of:
    diseased person, sick person, sufferer
    a person suffering from an illness
  2. noun
    a reckless impetuous irresponsible person
    see moresee less
    types:
    tearaway
    a reckless and impetuous person
    type of:
    adventurer, venturer
    a person who enjoys taking risks
  3. adjective
    insane and believed to be affected by the phases of the moon
    synonyms: moonstruck
    insane
    afflicted with or characteristic of mental derangement
Cite this entry
Style:
MLA
  • MLA
  • APA
  • Chicago

Copy citation
DISCLAIMER: These example sentences appear in various news sources and books to reflect the usage of the word ‘lunatic'. Views expressed in the examples do not represent the opinion of Vocabulary.com or its editors. Send us feedback
Word Family