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n. pl. ir·ra·tion·al·i·ties
1. The state or quality of being irrational.
2. An irrational idea, expression, or act.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(ɪˌræʃəˈnælɪtɪ) or


1. the state or quality of being irrational
2. irrational thought, action, or behaviour
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ɪˌræʃ əˈnæl ɪ ti)

n., pl. -ties.
1. the quality or condition of being irrational.
2. an irrational action, thought, etc.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.




beside one-self In an intensely emotional state; unable to control or contain one’s feelings; highly excited. Though one may be beside one-self with feelings ranging from pleasure to rage, the essence of the state is irrationality—being out of one’s wits. The phrase is akin to the French hors de soi, and both relate to the concepts of being possessed or transported. Caxton used the expression in the late 15th century.

coop-happy Insane from confinement; stir-crazy; punch-drunk from being cooped up. Coop ‘a confined area,’ is also a slang term for jail. Happy is used euphemistically in this phrase to mean dull-witted or “feeling no pain,” whence the term.

flip one’s lid To react wildly or enthusiastically; to be delighted or outraged; to be knocked off one’s feet or bowled over with shock; to lose one’s head. This relatively new slang phrase of American origin plays with the idea that a “lid” serves to prevent something from escaping—in this case one’s common sense and control. Thus, to “flip one’s lid” is to lose self-control, leaving one unbalanced or crazed.

Present war emergencies plus strain and stress seem to have been too much for local governmental officials. I fear they have flipped their lids. (Letter to the editor, Ithaca, N.Y., Journal, January 30, 1951)

Currently, flip is heard more frequently than the longer flip one’s lid.

Our food and service are great. Our decor’s delightful. Your club treasurer will flip over our low rates. (Boston Globe, May 18, 1967)

Another variant, flip out, implies a more serious degree of losing control, as from drugs, a nervous breakdown, etc. It is analogous to freak out and go off the deep end in flavor and usage.

go bananas To go wild with excitement or rage, to act in an irrational or uncontrollable manner. The phrase supposedly comes from the chattering antics of a hungry monkey at the sight of a banana. It is nearly always used hyperbolically to indicate reason temporarily overcome by emotion; rarely would it be used to describe true mental derangement or disturbance.

go haywire See DISORDER

go off the deep end To overreact, to get inappropriately angry or excited; to go overboard, to overdo it; to go in over one’s head; to freak out. The “deep end” refers to the end of a swimming pool at which the water is deepest. Floundering unprepared and confused in the “deep end,” one is apt to behave wildly and without a sense of propriety or concern for appearances. Dating from the early 1900s, this expression most often describes emotional outbursts, including occasionally those severe enough to be classified as mental breakdown.

lose one’s head To lose one’s equilibrium or presence of mind; to be out of control, off balance, or beside one-self. The head is associated with reason, sense, and rationality. Thus, to “lose one’s head” is to become irrational and out of control. Its figurative use dates from the 1840s.

It has now and then an odd Gallicism—such as “she lost her head,” meaning she grew crazy. (Edgar Allan Poe, Marginalia, 1849)

The phrase is often used to explain behavior (such as a temper tantrum or show of affection) that would otherwise be considered out of character or inappropriate.

lose one’s marbles To go crazy; to act or speak in an irrational manner. Since the early 1900s, marbles has been equated with common sense and mental faculties. Therefore, to lose one’s marbles is to lose one’s wits, especially when there has been a sudden behavioral change which manifests itself in eccentric or irrational acts or babblings.

You lost your goddam’ marbles? You gone completely crazy, you nutty slob? (J. Wainwright, Take-Over Men, 1969)

A related expression is have some marbles missing.

mad as a hatter Crazy, insane, demented; stark raving mad; violently angry, livid, venomous. It is probable that this expression is a corruption of mad as an atter, in which after is an Anglo-Saxon variation of adder ‘viper,’ a poisonous snake. Thus, the original expression implied that a person was venomous, ready to strike with malicious intent. One source suggests that mad as a hatter may allude to the insanity and loss of muscular control caused by prolonged exposure to mercurous nitrate, a chemical once commonly used in the manufacture of felt hats. At any rate, in current usage, mad as a hatter refers to lunacy more often than to anger.

In that direction … lives a Hatter; and in that direction … lives a March hare … They’re both mad. (Lewis Carroll, Alice’s Adventures in Wonderland, 1865)

mad as a March hare Agitated, excited, worked up; frenzied, wild, erratic; rash; insane, crazy. This expression probably alludes to the behavior of hares during mating season when they thump the ground with their hind legs, and jump up and down, twisting their bodies in midair. Several sources suggest that the original expression may have been mad as a marsh hare, implying that due to lack of protective shrubbery in marshes, these hares act more wildly than others.

As mad not as a March hare, but as a mad dog. (Sir Thomas More, The Supplycacyon of Soulys, 1529)

This expression was undoubtedly the inspiration for the March hare in Lewis Carroll’s Alice’s Adventures in Wonderland (1865). A common variation is wild as a March hare. The related term harebrained describes a person who is reckless or eccentric, or a plan, scheme, project, or other matter that is of dubious merit.

Whilst they, out of hare-brained lunacy, desire battle. (John Stephans, Satyrical Essays, Characters, and Others, 1615)

stir-crazy To behave neurotically as a result of long-term imprisonment; to be climbing the walls; to act dull-witted or punch-drunk from confinement. Stir is a slang term for jail or prison. Although originating as underworld lingo, stir is now fairly common, especially in the phrase stir-crazy which is no longer limited in use to prison-related neurosis. Rather, any lack of activity or temporary isolation can make one stir-crazy. The term is rarely if ever used literally —almost always hyperbolically.

Picturesque Expressions: A Thematic Dictionary, 1st Edition. © 1980 The Gale Group, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.irrationality - the state of being irrationalirrationality - the state of being irrational; lacking powers of understanding
insanity - relatively permanent disorder of the mind
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.


noun senselessness, madness, insanity, absurdity, lunacy, lack of judgment, illogicality, unreasonableness, preposterousness, unsoundness, brainlessness the irrationality of his behaviour
Collins Thesaurus of the English Language – Complete and Unabridged 2nd Edition. 2002 © HarperCollins Publishers 1995, 2002


The American Heritage® Roget's Thesaurus. Copyright © 2013, 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


[ɪˌræʃəˈnælɪtɪ] Nirracionalidad f
Collins Spanish Dictionary - Complete and Unabridged 8th Edition 2005 © William Collins Sons & Co. Ltd. 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005


[ɪˌræʃəˈnælɪti] n [feeling, idea, argument, behaviour] → irrationalité f
Collins English/French Electronic Resource. © HarperCollins Publishers 2005


n (= illogicality, Math, Psych) → Irrationalität f; (of fear, belief)Unsinnigkeit f, → Irrationalität f; (= lack of good sense)Unvernünftigkeit f
Collins German Dictionary – Complete and Unabridged 7th Edition 2005. © William Collins Sons & Co. Ltd. 1980 © HarperCollins Publishers 1991, 1997, 1999, 2004, 2005, 2007
References in classic literature ?
"I suppose you are always interfering with your own feelings,and those of other people, and dogmatizing about the irrationality of this, that, and the other sentiment, and then ordering it to be suppressed because you imagine it to be inconsistent with logic."
His injustice and ill-humour towards his inferiors, who could not defend themselves, I still resented and withstood; but when I alone was their object, as was frequently the case, I endured it with calm forbearance, except at times, when my temper, worn out by repeated annoyances, or stung to distraction by some new instance of irrationality, gave way in spite of myself, and exposed me to the imputations of fierceness, cruelty, and impatience.
He had ceased drinking at a point below irrationality, and had neither stirred nor spoken during two or three hours.
'Interference with the decision making process is warranted where it is vitiated on account of arbitrariness, illegality, irrationality and procedural impropriety or where it is actuated by malafides.
Salzman's special concern is the resurgence of irrationality, anti-intellectualism and anti-science attitudes..
In this groundbreaking book, Andrew Lo transforms the debate with a powerful new framework in which rationality and irrationality coexist -- the Adaptive Markets Hypothesis, says a review on the Princeton University Press website.
It is no surprise that Akel, the par excellence exponent of irrationality in Cyprus, is at the forefront of this ignoble cause.
Goulston, a psychiatrist, business advisor, mentor, speaker, and author, offers a guide to dealing with irrational people by leaning into the irrationality. He explains how to recognize that the person is unable to think rationally in the current situation; identify the way he or she acts out the irrationality; realize that the crazy behavior isn't about oneself; talk with the rational person, leaning into his or her crazy by entering the world calmly and with intention; show the person that one is an ally rather than a threat; and help him or her to a saner way of thinking when calm.
The imagery was morbid in some of the images and pleasant in some others but on the whole the work was suggestive of human irrationality.
'Stifling criticisms and shunning international condemnation, irrationality of behavior and policies, constant animosity towards the Church, sell-out of our sovereign rights over our maritime domain, and rejection of accountability for the heinous acts of summary killings-these are a clear recipe for self-destruction.'
A provocative shift in perspective at the midway point, however, calls the irrationality of those young neuroses into question: It's a gambit that may divide auds, but leaves little doubt as to the expertise of the film's directorial manipulation.
for those who criticize politically-correct irrationality.