Ir*ra"tion*al (?), a. [L.
irrationalis: cf. F. irrationnel. See In- not,
and Rational.]
1. Not rational; void of reason or
understanding; as, brutes are irrational animals.
2. Not according to reason; absurd;
foolish.
It seemed utterly irrational any longer to
maintain it.
I. Taylor.
3. (Math.) Not capable of being
exactly expressed by an integral number, or by a vulgar fraction;
surd; -- said especially of roots. See Surd.
Syn. -- Absurd; foolish; preposterous; unreasonable;
senseless. See Absurd.