irrational

adjective

ir·ra·tio·nal | \ i-ˈra-sh(ə-)nəl ,

ˌi(r)- \

Definition of irrational

(Entry 1 of 2)

: not rational: such as

a(1) : not endowed with reason or understanding

(2) : lacking usual or normal mental clarity or coherence

b : not governed by or according to reason irrational fears

c Greek & 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

irrational

noun

Definition of irrational (Entry 2 of 2)

1 : an irrational being

2 : irrational number

Other Words from irrational Synonyms & Antonyms Example Sentences Learn More about irrational

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Other words from irrational

Adjective

irrationality \i-ˌra-shə-ˈna-lə-tē,

ˌi(r)- \ noun

irrationally \i-ˈra-sh(ə-)nə-lē,

ˌi(r)- \ adverb

Examples of irrational in a Sentence

Adjective

He became irrational as the fever got worse. She had an irrational fear of cats.

Recent Examples on the Web: Adjective

This raised the question of whether the process is irrational or is, in some way, a purposeful evolutionary advantage. — Maya Miller, Scientific American, "Why It’s So Hard to Junk Bad Decisions—Edging Closer to Understanding “Sunk Cost”," 12 July 2018 Then there’s irrational stressing out about things that are unlikely to happen, like a terrorist attack. — Carolyn L. Todd, SELF, "7 Tips for Managing Your Anxiety About Traveling," 17 May 2018 Open borders is a radical, irrational idea that cannot be accepted. — sacbee, "Text of AG Sessions’ Sacramento speech | The Sacramento Bee," 7 Mar. 2018 Trump used to claim he would be vindicated, and his advisers insisted his periodic fits sprang from an irrational resentment that Mueller was tarnishing his election and obscuring his achievements. — Jonathan Chait, Daily Intelligencer, "Will Trump Be Meeting With His Counterpart — Or His Handler?," 8 July 2018 That’s an irrational argument which is very difficult to argue against or even to understand in the first instance. — Jeremy Eichler, BostonGlobe.com, "Music from the shadows, being heard anew," 28 June 2018 The Parkland activists have been subject to vicious, irrational attacks from right-wingers ever since the movement's inception. — refinery29.com, "Stoneman Douglas Activist David Hogg's Family Was "Swatted"," 5 June 2018 The irrational fear of the number 13 is now called triskaidekaphobia. — Lily Puckett, Teen Vogue, "8 Origins, Myths, and Superstitions That Explain Friday the 13th," 12 July 2018 This precise irrational rationale is the intellectual formula of choice for budding totalitarian regimes. — Laurie Penny, Longreads, "Peterson’s Complaint," 12 July 2018

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