insanity

noun
in·​san·​i·​ty | \ in-ˈsa-nə-tē How to pronounce insanity (audio) \
plural insanities

Definition of insanity

1 dated : a severely disordered state of the mind usually occurring as a specific disorder
2 law : unsoundness of mind or lack of the ability to understand that prevents one from having the mental capacity required by law to enter into a particular relationship, status, or transaction or that releases one from criminal or civil responsibility
3a : extreme folly or unreasonableness the insanity of violence His comments were pure insanity.
b : something utterly foolish or unreasonable the insanities of modern life

Keep scrolling for more

Synonyms & Antonyms for insanity

Synonyms

aberration, dementia, derangement, lunacy, madness, mania, rage [archaic]

Antonyms

mind, saneness, sanity

Visit the Thesaurus for More 

On the Meaning of Insanity

An oft-quoted bon mot (frequently attributed to Albert Einstein, Benjamin Franklin, or a number of other people who probably never said it) is that insanity may be defined as “doing the same thing over and over and expecting different results.” While the job of lexicographers might be easier if they were allowed to use witty sayings instead of precise definitions, such belletristic labors are not within their purview. The straight facts about insanity are these: it has been in use in English since the late 16th century, for the first two hundred years or so carrying only the literal meaning “the condition of being mentally deranged.” In the 19th century it began to take on a looser sense, “extreme folly or unreasonableness.” In modern usage, insanity may be found in both senses: you may tell your brother that trying to skateboard while holding onto a car is "insanity" (in which case you mean that it is extremely foolish) or encounter the stricter original meaning in such contexts as insanity plea.

Examples of insanity in a Sentence

She was found not guilty by reason of insanity. His friends thought his decision to quit his job was pure insanity. Please, no more violence. It's time to stop this insanity. the insanities of modern life
See More

Recent Examples on the Web

Hurt was involuntarily committed for treatment to the Elgin facility in 2014 after he was found not guilty by reason of insanity for felony aggravated battery of an Aurora peace officer. CBS News, "Social worker charged with sexual misconduct at Illinois mental health center," 6 Apr. 2018 Earlier this week, the prosecution rested its case against Ortega, who is pleading not guilty by reason of insanity for allegedly stabbing the children in the bathtub of their Upper West Side apartment on Oct. 25, 2012. Kc Baker, PEOPLE.com, "N.Y.C. Nanny Accused of Murdering 2 Kids in Her Care Sounded Like 'Demon' Hours Before, Says Sister," 22 Mar. 2018 When Virginia guard Kyle Guy stepped to the foul line with 0.6 second left, an NCAA tournament’s worth of insanity had taken place in the prior five minutes alone. Andrew Beaton, WSJ, "Virginia Advances in NCAA Final Four to National Championship Game," 6 Apr. 2019 Memories of the insanity just beyond the store's walls quickly evaporated as guests wandered further into the party. Mai Morsch, Vogue, "The Fashion Week Weary Found Refuge at DVF's Botanical Oasis," 11 Feb. 2019 Whether Sawyer is in the grip of insanity or a hellish trap of legitimate physical danger, Unsane is a dispiritingly pedestrian woman-in-peril shocker to have come from such a maverick filmmaker. David Rooney, The Hollywood Reporter, "'Unsane': Film Review | Berlin 2018," 21 Feb. 2018 Asking someone to jump in a shark tank for the sake of fashion is an exercise in insanity. Laura Brown, Harper's BAZAAR, "Rihanna: The Interview," 5 Feb. 2015 Along those lines, female insanity or hysteria has historically been tied to their reproductive organs. Chloe Schama, Vogue, "How Laura Sims Turned the “Torturous Limbo” of Infertility Into Fascinating Fiction," 11 Jan. 2019 More importantly, this film remains grounded through its gorgeously drawn insanity by focusing on newest hero Miles Morales and his emotional relationships with imperfect mentors. 1. Sam Machkovech And Nathan Mattise, Ars Technica, "Films for the discerning nerd: Ars picks the best of 2018," 27 Dec. 2018

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

See More

First Known Use of insanity

1590, in the meaning defined at sense 1

Keep scrolling for more

Learn More about insanity

Statistics for insanity

Last Updated

15 May 2019

Look-up Popularity

Time Traveler for insanity

The first known use of insanity was in 1590

See more words from the same year

Keep scrolling for more

More Definitions for insanity

insanity

noun

English Language Learners Definition of insanity

: severe mental illness : the condition of being insane
: something that is very foolish or unreasonable

insanity

noun
in·​san·​i·​ty | \ in-ˈsa-nə-tē How to pronounce insanity (audio) \

Kids Definition of insanity

: the condition of being abnormal or unhealthy in mind

insanity

noun
in·​san·​i·​ty | \ in-ˈsan-ət-ē How to pronounce insanity (audio) \
plural insanities

Medical Definition of insanity

1 dated : a severely disordered state of the mind usually occurring as a specific disorder
2 law : unsoundness of mind or lack of the ability to understand that prevents one from having the mental capacity required by law to enter into a particular relationship, status, or transaction or that releases one from criminal or civil responsibility

Keep scrolling for more

insanity

noun
in·​san·​i·​ty

Legal Definition of insanity

1 : unsoundness of mind or lack of the ability to understand that prevents one from having the mental capacity required by law to enter into a particular relationship, status, or transaction or that releases one from criminal or civil responsibility: as
a : a disease, defect, or condition of the mind that renders one unable to understand the nature of a criminal act or the fact that it is wrong or to conform one's conduct to the requirements of the law being violated
b : inability to understand and participate in legal proceedings brought against one : incompetence
c : inability to understand the nature and purpose of a punishment (as the death penalty) to which one has been sentenced
d : inability to understand the nature and consequences of one's acts (as making a will) or of events, matters, or proceedings in which one is involved — see also commitment, durham rule, irresistible impulse test, m'naghten test, not guilty by reason of insanity, substantial capacity test — compare capacity, competency, competent, diminished capacity, sanity
2 : the affirmative defense of having acted while insane

Keep scrolling for more

Comments on insanity

What made you want to look up insanity? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

something valued as if it were money

Get Word of the Day daily email!

Test Your Vocabulary

Time Traveler Quiz: Which Word Came First?

  • time traveler quiz which word came first
  • Which came first?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

TAKE THE QUIZ
Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ
Love words? Need even more definitions?

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