Meaning of “irrational” - Learner’s Dictionary

irrational

adjective uk us /ɪˈræʃənəl/

Irrational feelings and actions are based on your emotions and not on good reasons:

irrational behaviour
an irrational fear of flying
irrationality uk us /ɪˌræʃənˈæləti/ noun [ U ]
irrationally adverb

(Definition of “irrational” from the Cambridge Learner’s Dictionary © Cambridge University Press)