Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English

English definition of “irrational”

irrational

adjective  /ɪˈræʃ·ə·nəl/ us  
not based on reason or clear thinking; not reasonable: One of her main themes is the irrational nature of love.
(Definition of irrational from the Cambridge Academic Content Dictionary © Cambridge University Press)
What is the pronunciation of irrational?
Browse related topics

You are looking at an entry to do with Of unsound mind, but you might be interested in these topics from the Psychology, psychiatry, & psychoanalysis topic area:

Add Cambridge dictionaries to your browser to your website

More American English definitions for “irrational”

Definitions of “irrational” in other dictionaries

Word of the Day

nip

to press something quickly and quite hard between two objects, especially sharp objects such as teeth or nails

Word of the Day

Blog

Read our blog about how the English language behaves.

Learn More

New Words

Find words and meanings that have just started to be used in English, and let us know what you think of them.

Learn More