lunacy

noun

lu·​na·​cy ˈlü-nə-sē 

plural lunacies

1

dated

a

: insanity sense 1

b

: intermittent insanity once believed to be related to phases of the moon

2

: wild foolishness : extravagant folly

3

: a foolish act

Synonyms

• absurdity
• asininity
• bêtise
• fatuity
• folly
• foolery
• foppery
• idiocy
• imbecility
• inanity
• insanity
• stupidity

Examples of lunacy in a Sentence

Quitting her job was lunacy.

His idea was considered total lunacy.

Recent Examples on the Web

This is Orwellian, and everyone in Europe and the U.S. must reject this lunacy. —Josh Hammer, Newsweek, 17 Feb. 2025

Every cold open featuring Harris and her cohort just rehashed each week’s news cycle, with throwaways to Johnson’s Trump and Bowen Yang as J.D. Vance featuring the two often just reciting actual statements made along the campaign trail, as if the lunacy of it all couldn’t be made more ridiculous. —Harrison Richlin, IndieWire, 15 Feb. 2025

The cast try their best to keep up with such lunacy. —Jon O'Brien, IndieWire, 16 Jan. 2025

There’s always been pushback against anti-immigrant lunacy here. —Gustavo Arellano, Los Angeles Times, 30 Jan. 2025

Word History

Etymology

lun(atic) + -acy

First Known Use

1541, in the meaning defined at sense 1a

Kids Definition

lunacy

noun

lu·​na·​cy ˈlü-nə-sē 

plural lunacies

: insanity sense 1

—used chiefly in the past

Medical Definition

lunacy

noun

lu·​na·​cy ˈlü-nə-sē 

plural lunacies

dated

: mental illness

also : intermittent mental illness once believed to be related to phases of the moon

Legal Definition

lunacy

noun

lu·​na·​cy ˈlü-nə-sē 

: insanity