insanity

noun

in·​san·​i·​ty in-ˈsa-nə-tē How to pronounce insanity (audio)
plural insanities
1
dated : a severely disordered state of mind usually occurring as a specific disorder
2
law : unsoundness of mind or lack of the ability to understand that prevents someone from having the mental capacity required by law to enter into a particular relationship, status, or transaction or that releases someone from criminal or civil responsibility
3
a
: extreme folly or unreasonableness
the insanity of violence
His comments were pure insanity.
b
: something utterly foolish or unreasonable
the insanities of modern life

Did you know?

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.

Example Sentences

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
Recent Examples on the Web Reddington said a person whom experts conclude was overmedicated at the time of a crime can invoke a defense of not guilty by reason of insanity. Laura Crimaldi, BostonGlobe.com, 3 Feb. 2023 Yates was initially convicted of murder before that conviction was overturned and she was found not guilty by reason of insanity in 2006. Julianne Mcshane, NBC News, 30 Jan. 2023 People who are found not guilty by reason of insanity are then committed to the custody of the PSRB, which oversees each patient’s case for the length of their commitment. Taylor Hartz, Hartford Courant, 27 Jan. 2023 As the saying goes, the definition of insanity is to do the same thing over and over again and expect different results. Yec, Forbes, 26 Jan. 2023 By this standard, both Sri Lanka and the IMF crossed the threshold of insanity long, long ago. Caleb Hofmann, National Review, 18 Jan. 2023 Several lawmakers have made a joke about the definition of insanity (doing the same thing over and over again while expecting different results). Amanda Kaufman, BostonGlobe.com, 7 Jan. 2023 Du, 25, has pleaded not guilty by reason of insanity to attempted murder of a police officer in the April 27 shooting of CHP Officer Tony Pacheco. Andrew Joseph Garcia, San Diego Union-Tribune, 3 Jan. 2023 Its patients include some criminal defendants awaiting competency hearings or found not guilty by reason of insanity. Justin Wm. Moyer, Washington Post, 23 Dec. 2022 See More

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.

Word History

First Known Use

1590, in the meaning defined at sense 1

Time Traveler
The first known use of insanity was in 1590

Dictionary Entries Near insanity

Cite this Entry

“Insanity.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/insanity. Accessed 9 Feb. 2023.

Kids Definition

insanity

noun
in·​san·​i·​ty in-ˈsan-ət-ē How to pronounce insanity (audio)
plural insanities
1
: the condition of being insane especially when serious enough to keep one from being convicted of a crime or from performing duties required by law
2
a
: extreme foolishness or unreasonableness
b
: senseless conduct

Medical Definition

insanity

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

Legal Definition

insanity

noun
in·​san·​i·​ty
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

More from Merriam-Webster on insanity

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