lu·​na·​cy | \ ˈlü-nə-sē How to pronounce lunacy (audio) \
plural lunacies

Definition of lunacy

1 dated
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 in a Sentence

Quitting her job was lunacy. His idea was considered total lunacy.
Recent Examples on the Web All of this is just very inefficient and frankly, in a lot of cases, just lunacy and completely illogical, to rely on mass chaos as a distribution strategy. Dave Knox, Forbes, 2 May 2022 This content can be found in both quick sight gags and elaborately staged lunacy—along with out-of-body camera-angle trickery new to the series. Sam Machkovech, Ars Technica, 27 Apr. 2022 Even the set dressing occasionally succumbs to lunacy. Amy Nicholson, WSJ, 24 Mar. 2022 Hader and Berg, who split directing duties on the first six episodes, continue to make refinements to the show’s love of extended gags that blend action and lunacy. Daniel Fienberg, The Hollywood Reporter, 19 Apr. 2022 College football remains the premier home for lunacy. Jacob Carpenter, Fortune, 18 Apr. 2022 Gyllenhaal recently took home a raft of Gotham Independent Spirit Awards and Golden Globe nominations for catering to our Christine Blasey Ford culture no matter the lunacy. Armond White, National Review, 17 Dec. 2021 Such lunacy makes common decency difficult to summon and act upon. Richard Russo, The Atlantic, 9 Mar. 2022 This is an astonishing level of support for sheer lunacy. John Ellis, WSJ, 14 Jan. 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'lunacy.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of lunacy

1541, in the meaning defined at sense 1a

History and Etymology for lunacy


Learn More About lunacy

Dictionary Entries Near lunacy



luna moth

See More Nearby Entries 

Statistics for lunacy

Last Updated

23 May 2022

Cite this Entry

“Lunacy.” Dictionary, Merriam-Webster, Accessed 27 May. 2022.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

More Definitions for lunacy


lu·​na·​cy | \ ˈlü-nə-sē How to pronounce lunacy (audio) \
plural lunacies

Medical Definition of lunacy

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


lu·​na·​cy | \ ˈlü-nə-sē How to pronounce lunacy (audio) \

Legal Definition of lunacy

More from Merriam-Webster on lunacy

Nglish: Translation of lunacy for Spanish Speakers

Britannica English: Translation of lunacy for Arabic Speakers


Test Your Vocabulary

Eponyms: Words Named After People

Spell It

Can you spell these 10 commonly misspelled words?

Universal Daily Crossword

A daily challenge for crossword fanatics.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!