noun, plural ir·ra·tion·al·i·ties for 2.

the quality or condition of being irrational.
an irrational, illogical, or absurd action, thought, etc.

Origin of irrationality

First recorded in 1560–70; irrational + -ity Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for irrationality

Contemporary Examples of irrationality

  • After all, doing so would make them complicit in irrationality, which is against their religion.

    The Daily Beast logo
    In Florida, ’Tis The Season for Satan

    Jay Michaelson

    December 7, 2014

  • There is an honorable dimension to daring rooted in vanity, to reckless boldness, to irrationality in the service of an ideal.

    The Daily Beast logo
    Why There Will Always Be Weiners

    Lee Siegel

    June 17, 2011

  • Reality television has never been tame, but aggression, irrationality, and even violence is on the increase.

    The Daily Beast logo
    Reality TV's Violent Turn

    Andy Dehnart

    November 18, 2010

  • The act itself is grounded in irrationality, so it often defies rational explanations.

    The Daily Beast logo
    What Haunted Freddie's CFO?

    Charlie Gasparino

    April 23, 2009

  • Ignorance is a lack of information, not a genetic defect or a “cultural style;” and irrationality should be fought at every step.

    The Daily Beast logo
    A Great Black Actor Goes Loco

    Stanley Crouch

    April 10, 2009

Historical Examples of irrationality

  • But machines could not hope to encompass all the irrationality of Man.

    Mezzerow Loves Company

    Floyd L. Wallace

  • Elsmere's irrationality was an aversion to doctors, from the point of view of his own ailments.

    Robert Elsmere

    Mrs. Humphry Ward

  • This is the fifth example of irrationality and incommensurability.

  • This is the fourth example of irrationality, or incommensurability.

  • The irrationality of the defence was a final proof that the lawyer had played him false.

    Gulmore, The Boss

    Frank Harris

British Dictionary definitions for irrationality




the state or quality of being irrational
irrational thought, action, or behaviour
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for irrationality

1560s, from irrational + -ity.

Online Etymology Dictionary, © 2010 Douglas Harper