IRRA'TIONAL, adjective [Latin irrationalis; in and rationalis, from ratio.] 1. Not rational; void of reason or understanding. Brutes are irrational animals. 2. Not according to the dictates of reason; contrary to reason; absurd. To pursue a course of life which destroys happiness, is irrational
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI