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English definition of “irrational”

irrational

adjective uk   /ɪˈræʃ.ən.əl/ us  
C2 not using reason or clear thinking: It's totally irrational, but I'm frightened of mice. His parents were worried by his increasingly irrational behaviour.Of unsound mindStupid and silly
irrationally
adverb uk   /-i/ us  
People often behave irrationally when they are under stress.Of unsound mindStupid and silly
irrationality
noun [U] uk   /ɪˌræʃ.ənˈæl.ə.ti/ us    /-t̬i/
Of unsound mindStupid and silly
(Definition of irrational from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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