not based on, or not using, clear logical thought synonym unreasonable an irrational fear You're being irrational. opposite rational
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NAmE//ɪˌræʃəˈnælət̮i//
noun [uncountable, countable, usually singular] NAmE//ɪˈræʃənəli//
adverb to behave irrationallySee irrational in the Oxford Advanced Learner's DictionaryCheck pronunciation: irrational