irrational
adj. B2 Upper Intermediate US //ˌɪˈɹæʃənəɫ// UK //ɪɹˈæʃənəl// ir·ra·tional
adj. not based on reason or logic. You use this to describe thoughts, feelings, or actions that do not make sense.
adj. not guided by or based on reason or logic; characterized by a lack of rational thought. Often used to describe emotions, decisions, or behavior that defies logical explanation.
It was an irrational fear of spiders.
She made an irrational decision to quit her job without a backup plan.
The market's irrational exuberance eventually led to a sharp correction in stock prices.
From Latin irratiōnālis, from ir- + ratiōnālis.