irrational
1 of 2adjective
ir·ra·tio·nal i-ˈra-sh(ə-)nəl 
ˌi(r)-
: not rational: such as
a(1)
: lacking usual or normal mental clarity or coherence
(2)
: not endowed with reason or understanding
b
: not governed by or according to reason
irrational fears
c Greek and Latin prosody
(1)
of a syllable : having a quantity other than that required by the meter
(2)
of a foot : containing such a syllable
d(1)
: being an irrational number
an irrational root of an equation
(2)
: having a numerical value that is an irrational number
a length that is irrational
irrationality
i-ˌra-shə-ˈna-lə-tē
noun ˌi(r)-
irrationally
i-ˈra-sh(ə-)nə-lē
adverb ˌi(r)-
irrational
2 of 2noun
1
: an irrational being
2
: irrational number
Synonyms
Adjective
- fallacious
- illegitimate
- illogical
- inconsequent
- inconsequential
- invalid
- nonrational
- unreasonable
- unreasoning
- unsound
- weak
See all Synonyms & Antonyms 
Example Sentences
Adjective He became irrational as the fever got worse. She had an irrational fear of cats.
Recent Examples on the Web
Anna Hirtenstein, WSJ, 24 Aug. 2022 It’s not irrational to find deals including pizza for $3.14 this Monday. Kelly Tyko, USA TODAY, 14 Mar. 2022 What’s irrational is to pretend that such risks do not exist. James Freeman, WSJ, 9 Mar. 2022 It’s not irrational to find pizza pies for $3.14 this Sunday. Kelly Tyko, The Arizona Republic, 14 Mar. 2021 Talk back to the worries that are irrational, reminding yourself of past transitions that worked out well. Rachel Feintzeig, WSJ, 22 Aug. 2022 On the other hand, unfounded optimism can also lead to irrational investment decisions. Q.ai - Make Genius Money Moves, Forbes, 18 Oct. 2021 Scientists frequently accuse those who reject their findings of being irrational. Naomi Oreskes, Scientific American, 20 July 2022 Because scapegoating is irrational, offenders often will target someone who happens to be nearby. Katherine Kam, Washington Post, 19 July 2022 Alison Fishburn, Longreads, 17 Sep. 2022 On the back of the acquisitions of AirTerra and Quiet Logistics in 2021, AEO seemed to do the irrational by bringing onstream capacities and capabilities that significantly exceeded its own item demand. Niall Murphy, Forbes, 17 June 2022 The moral, social, and epistemic void in which Germans found themselves after defeat was filled, at least for a time, by the irrational. Richard J. Evans, The New Republic, 1 Dec. 2021 As such, any attempt to explain it will run sooner or later into the wall of the irrational. Phil Klay, Harper's Magazine, 23 Nov. 2021 But feeling anxious right now is not at all out of line or irrational. Jessica Dulong, CNN, 31 Aug. 2021 Attempting to appease the loudest to the detriment of the community only emboldens the irrational and silences those looking to have productive conversation. Benjamin Ayanian, Star Tribune, 5 May 2021 To believe in the return of a long-dead child reflects the anguish of the believer and, of course, a tendency to embrace the irrational. Dorothy Rabinowitz, WSJ, 29 Apr. 2021 We are all steered by a mixture of the rational and the irrational. Christopher Beha, Harpers Magazine, 5 Jan. 2021 See More
Adjective
The market is irrational and the combination of decent demand, falling inventories and tight supply should be pushing prices up, Goldman Sachs analysts said in an Aug. 12 report. Anna Hirtenstein, WSJ, 24 Aug. 2022 It’s not irrational to find deals including pizza for $3.14 this Monday. Kelly Tyko, USA TODAY, 14 Mar. 2022 What’s irrational is to pretend that such risks do not exist. James Freeman, WSJ, 9 Mar. 2022 It’s not irrational to find pizza pies for $3.14 this Sunday. Kelly Tyko, The Arizona Republic, 14 Mar. 2021 Talk back to the worries that are irrational, reminding yourself of past transitions that worked out well. Rachel Feintzeig, WSJ, 22 Aug. 2022 On the other hand, unfounded optimism can also lead to irrational investment decisions. Q.ai - Make Genius Money Moves, Forbes, 18 Oct. 2021 Scientists frequently accuse those who reject their findings of being irrational. Naomi Oreskes, Scientific American, 20 July 2022 Because scapegoating is irrational, offenders often will target someone who happens to be nearby. Katherine Kam, Washington Post, 19 July 2022 Noun
But riveted mankind is hopelessly addicted to the irrational, with reliably disastrous results, planetwide. Alison Fishburn, Longreads, 17 Sep. 2022 On the back of the acquisitions of AirTerra and Quiet Logistics in 2021, AEO seemed to do the irrational by bringing onstream capacities and capabilities that significantly exceeded its own item demand. Niall Murphy, Forbes, 17 June 2022 The moral, social, and epistemic void in which Germans found themselves after defeat was filled, at least for a time, by the irrational. Richard J. Evans, The New Republic, 1 Dec. 2021 As such, any attempt to explain it will run sooner or later into the wall of the irrational. Phil Klay, Harper's Magazine, 23 Nov. 2021 But feeling anxious right now is not at all out of line or irrational. Jessica Dulong, CNN, 31 Aug. 2021 Attempting to appease the loudest to the detriment of the community only emboldens the irrational and silences those looking to have productive conversation. Benjamin Ayanian, Star Tribune, 5 May 2021 To believe in the return of a long-dead child reflects the anguish of the believer and, of course, a tendency to embrace the irrational. Dorothy Rabinowitz, WSJ, 29 Apr. 2021 We are all steered by a mixture of the rational and the irrational. Christopher Beha, Harpers Magazine, 5 Jan. 2021 See More Word History
Etymology
Adjective
Middle English, from Latin irrationalis, from in- + rationalis rational
First Known Use
Adjective
14th century, in the meaning defined above
Noun
1646, in the meaning defined at sense 1
Phrases Containing irrational
Kids Definition
irrational
adjective
ir·ra·tio·nal i-ˈra-shə-nᵊl
1
: not able to reason
The fever made him irrational.
2
: not based on reason
irrational fears
Medical Definition
irrational
adjective
ir·ra·tio·nal (ˈ)ir-ˈ(r)ash-nəl, -ən-ᵊl
: not rational: as
a
: lacking usual or normal mental clarity or coherence
was irrational for several days after the accident
b
: not governed by or according to reason
irrational fears
Legal Definition
irrational
adjective
ir·ra·tio·nal ir-ˈra-shə-nəl
: not rational: as
a
: not governed by reason, mental clarity, or understanding
b
: not governed by a fair consideration of facts or evidence
broadly : arbitrary
an irrational decision to deny the permit
irrationalities
noun
as in instabilities
Synonyms & Similar Words
Relevance
- instabilities
- insanities
- hysterias
- aberrations
- deliriums
- psychoses
- lunacies
- manias
- dementias
- neuroses
- derangements
- frenzies
- paranoias
- rages
- schizophrenias
- phobias
- obsessions
- delusions
- hallucinations
- abnormalities
- hypomanias
- hallucinoses
- senile dementias
- monomanias
Antonyms & Near Antonyms
- rationalities
- normalities
- lucidities
- minds
- reasonabilities