Noah Webster's Dictionary 1. (a.) Lacking reason or understanding; as, brutes are irrational animals. 2. (a.) Not according to reason; absurd; foolish. 3. (a.) Not capable of being exactly expressed by an integral number, or by a vulgar fraction; surd; -- said especially of roots. See Surd.

Multi-Version Concordance Irrational (3 Occurrences) Acts 25:27 for it doth seem to me irrational, sending a prisoner, not also to signify the charges against him.' (YLT) 2 Peter 2:12 and these, as irrational natural beasts, made to be caught and destroyed -- in what things they are ignorant of, speaking evil -- in their destruction shall be destroyed, (YLT RSV) Jude 1:10 But these, whatever things they know not, they speak railingly against; but what even, as the irrational animals, they understand by mere nature, in these things they corrupt themselves. (DBY YLT RSV)