delusional
adj. B2 Upper Intermediate US //dɪˈɫuʒənəɫ// UK //dɪlˈuːʒənəl// delu·sion·al
adj. believing something that is not true, even when you have clear proof that it is wrong. You use this word when someone refuses to accept reality.
adj. holding a fixed false belief despite evidence to the contrary; often used informally to describe unrealistic optimism or self-deception.
He is delusional about his chances of winning.
The manager remained delusional about the project's success despite mounting losses and staff complaints.
Critics argued that the politician's delusional view of public opinion blinded him to the growing unrest in the streets.
From delusion + -al.