• enPR: ĭră'sh(ə)nəl, IPA: /ɪˈɹæʃ.(ə.)nəl/


  1. Not rational; unfounded or nonsensical.
    an irrational decision
    • July 18, 2012, Scott Tobias, AV Club The Dark Knight Rises[,82624/]
      Where the Joker preys on our fears of random, irrational acts of terror, Bane has an all-consuming, dictatorial agenda that’s more stable and permanent, a New World Order that’s been planned out with the precision of a military coup.
  2. (mathematics, arithmetic, number theory, not comparable) Of a real number, that cannot be written as the ratio of two integers.
    The number π is irrational.
    Antonyms: rational
    hypo en
Translations Translations Noun

irrational (plural irrationals)

  1. A real number that can not be expressed as the quotient of two integers, an irrational number.
    • 1946, Bertrand Russell, History of Western Philosophy, I.24:
      The square root of 2, which was the first irrational to be discovered, was known to the early Pythagoreans, and ingenious methods of approximating to its value were discovered.

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