lunacy

American  

[loo-nuh-see] / ˈlu nə si /

noun

lunacies plural

1. insanity; mental disorder.

   Synonyms:

   aberration, mania, madness, craziness, dementia, derangement

   Antonyms:

   sanity, rationality

2. intermittent insanity, formerly believed to be related to phases of the moon.

   Antonyms:

   sanity, rationality

3. extreme foolishness or an instance of it.

   Her decision to resign was sheer lunacy.

   Synonyms:

   stupidity, folly

4. unsoundness of mind sufficient to incapacitate one for civil transactions: a former legal term.

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lunacy British  

/ ˈluːnəsɪ /

noun

1. (formerly) any severe mental illness

2. foolishness or a foolish act

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Other Word Forms

Inflected Forms

noun

• lunacies
  plural

Etymology

Origin of lunacy

First recorded in 1535–45; lun(atic) + -acy

Explanation

Lunacy is acting silly or stupid. Your mom might yell, "It's lunacy to go out in the snow wearing those flip flops!" Some people use the noun lunacy when they talk about actual mental instability, although this is considered old fashioned and outdated. It's much more common to describe the lunacy of someone who does something ridiculous or foolish. While adopting a cat from the animal shelter might be a great idea, adopting all thirty cats from the shelter would be lunacy. Lunacy comes from lunatic, originally "affected with periodic insanity, dependent on phases of the moon."

Related Words

• absurdity
• folly
• foolishness
• idiocy
• insanity
• mania
• silliness
• stupidity