Definition

1. Adjective:

   • Insane, mentally deranged: Describes a person who is suffering from severe mental illness, historically believed to be influenced by the moon's phases.
   • Wildly foolish, senseless: Describes an idea, action, or behavior that is extremely reckless, irrational, or foolish.

2. Noun:

   • An insane person: A person who is severely mentally ill (this term is now considered offensive and outdated in medical and polite contexts).
   • A wildly foolish or reckless person: A person who acts with extreme impetuosity, lack of judgment, or irresponsibility.

Usage Examples

• Adjective:

  • The general was criticized for his lunatic plan to invade without any supplies. (Describes a wildly foolish plan.)
  • In the past, people with epilepsy were sometimes thought to be lunatic. (Describes a person believed to be insane, using an outdated concept.)

• Noun:

  • The old asylum was said to house lunatics. (Refers to people considered insane; note the outdated and offensive nature of this usage.)
  • He drove like a lunatic, weaving through traffic at high speed. (Refers to a recklessly irresponsible person.)

Advanced Usage

• "lunatic fringe": A small group within a political or social movement holding extreme or fanatical views.
  • The candidate's sensible policies were often overshadowed by the lunatic fringe of his supporters.

Variants and Related Words

• Lunacy (noun): The state of being a lunatic; insanity. Also used to mean extreme foolishness.
  • It would be sheer lunacy to attempt that climb in a storm.
• Lunatical (adjective): An archaic variant of 'lunatic' as an adjective.

Synonyms

• Adjective (insane): Mad, deranged, psychotic (clinical).
• Adjective (foolish): Crazy, insane, daft, preposterous, idiotic.
• Noun (insane person): Madman, maniac, psychotic (clinical; note many synonyms are also offensive).
• Noun (reckless person): Maniac, hothead, daredevil.

Related Phrases

• Like a lunatic: Behaving with extreme recklessness or frenzy.
  • He was shouting like a lunatic.

Important Note on Usage

The term 'lunatic' originates from the historical belief (luna = moon) that insanity was caused or worsened by the moon. In modern English, its use to describe a person with mental illness is considered highly offensive, derogatory, and outdated. It is acceptable, though strong, when used informally as a hyperbolic adjective to criticize an idea or action as extremely foolish (a lunatic scheme), or as a noun for a wildly reckless person (a speed lunatic). For clinical contexts, terms like "person with a mental illness" are appropriate.

Adjective

1. insane and believed to be affected by the phases of the moon

Noun

1. a reckless impetuous irresponsible person
2. an insane person