irrational /(ĭr*răsh"ŭn*al)/

ir·ra·tion·al

irrational

a.
  1. Not rational; void of reason or understanding; as, brutes are irrational animals.
  2. Not according to reason; having no rational basis; clearly contrary to reason; easily disproved by reasoning; absurd; -- of assertions and beliefs.
    It seemed utterly irrational any longer to maintain it.
  3. Not capable of being exactly expressed by an integral number, nor by a ratio of integral numbers; surd; -- said especially of roots. See Surd. (Math.)