The meaning of IRRATIONAL is not rational. How to use irrational in a sentence.

IRRATIONAL definition: without the faculty of reason; deprived of reason. See examples of irrational used in a sentence.

IRRATIONAL definition: 1. not using reason or clear thinking: 2. (of a number) that cannot be expressed as the ratio of…. Learn more.

If you describe someone's feelings and behaviour as irrational, you mean they are not based on logical reasons or clear thinking. ...an irrational fear of science.

irrational (ɪˈræʃənəl) adj 1. inconsistent with reason or logic; illogical; absurd 2. incapable of reasoning

Jan 20, 2026 · Noun irrational (plural irrationals) (mathematics) A real number that can not be expressed as the quotient of two integers, an irrational number.

Definition of irrational adjective in Oxford Advanced Learner's Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more.