Simple Definition of lunacy
: extreme foolishness
: something that is very foolish
: extreme mental illness
Full Definition of lunacy
1 a : insanity b : intermittent insanity once believed to be related to phases of the moon
2 : wild foolishness : extravagant folly
3 : a foolish act
Examples of lunacy
Quitting her job was lunacy.
His idea was considered total lunacy.
Origin of lunacy
First Known Use: 1541
Seen and Heard
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