ir·ra·tio·nal /ɪˈræʃ(ə)nəl, ˌɪ(r)-/
ir·ra·tio·nal /(ˈ)ɪrˈ(r)æʃnəl, ənḷ/ 形容詞
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. Hence, of actions: foolish; unreasonable.
It seemed utterly irrational any longer to maintain it. --I. Taylor.
3. Math. Not capable of being exactly expressed by an integral number, nor by a ratio of integral numbers; surd; -- said especially of roots. See Surd.
Syn: -- Absurd; foolish; preposterous; unreasonable; senseless. See Absurd.
adj 1: not consistent with or using reason; "irrational fears";
"irrational animals" [ant: rational]
2: real but not expressible as the quotient of two integers;
"irrational numbers" [ant: rational]