Definitions for "irrational"
Not rational; void of reason or understanding; as, brutes are irrational animals.
Not according to reason; having no rational basis; clearly contrary to reason; easily disproved by reasoning; absurd; -- of assertions and beliefs.
Not capable of being exactly expressed by an integral number, nor by a ratio of integral numbers; surd; -- said especially of roots. See Surd.
Keywords:  foolish, unreasonable
foolish; unreasonable.