Irrational is defined as lacking reason or understanding.(adjective)
An example of irrational is a fear of a certain color.
The definition of an irrational is a number that cannot be expressed as a fraction.(noun)
An example of irrational is pi.
See irrational in Webster's New World College Dictionary
Origin: ME < L irrationalis: see in- & rational
See irrational in American Heritage Dictionary 4
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