folly
Americannoun
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the state or quality of being foolish; lack of understanding or sense.
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a foolish action, practice, idea, etc.; absurdity.
the folly of performing without a rehearsal.
- Synonyms:
- lunacy, madness, injudiciousness, indiscretion, foolishness, mistake, rashness, imprudence
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a costly and foolish undertaking; unwise investment or expenditure.
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Architecture. a whimsical or extravagant structure built to serve as a conversation piece, lend interest to a view, commemorate a person or event, etc.: found especially in England in the 18th century.
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follies, a theatrical revue.
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Obsolete. wickedness; wantonness.
noun
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the state or quality of being foolish; stupidity; rashness
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a foolish action, mistake, idea, etc
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a building in the form of a castle, temple, etc, built to satisfy a fancy or conceit, often of an eccentric kind
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(plural) theatre an elaborately costumed revue
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archaic
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evil; wickedness
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lewdness; wantonness
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Usage
What does folly mean? A folly is a foolish action. Follies can refer to various unwise practices, buildings with a purely ornamental purpose, or cabaret-style theatrical revues featuring lots of beautiful, dancing women.
Other Word Forms
Etymology
Origin of folly
First recorded in 1175–1225; Middle English folie, from Old French, derivative of fol, fou “foolish, mad”; equivalent to fool 1 + -y 3 ( def. )
Explanation
Folly is a noun that means "foolish or crazy behavior." It would be folly to spend all night playing video games when you have a difficult exam the next day. Folly comes from the Old French word folie meaning "madness, stupidity." It can describe the silly or nonsensical things you do, like the folly of trying to rush across town in the middle of a snowstorm. Or it can describe the trait that makes people act that way: the folly of an inexperienced driver who doesn't know you can't speed on snow-covered roads. Can you see the word fool in folly? Not a coincidence.
Vocabulary lists containing folly
This Week in Words: January 20 - 26, 2018
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"Common Sense," Vocabulary from the pamphlet
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Siddhartha
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
With this growth comes confidence, and with confidence comes, well, folly.
From MarketWatch • Apr. 30, 2026
Perhaps Thucydides had something to say about the folly of war that they wouldn’t have appreciated had they remained civilians.
From Salon • Apr. 19, 2026
The two men strolled around the grounds of the castle, taking in the pointless folly of the battlements and arrow slits.
From The Wall Street Journal • Mar. 25, 2026
It also sets up the acute psychology that drives Magellan: obsessive curiosity warping into enforced Christian conversion, a consequential folly to which the filmmaker adds his own historical take.
From Los Angeles Times • Jan. 9, 2026
On the first $4 billion of Howie Hubler’s $16 billion folly, the loss came to roughly $3.7 billion.
From "The Big Short" by Michael Lewis
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
