thoughts started swimming through his mind—he wanted to jump up and attack, beat him like he’d beaten Gaily after escaping the Maze.
James Dashner -- The Scorch Trials
not rational; i.e., lacking reason
More rarely, irrational numbers in mathematics are numbers that cannot be expressed as a fraction consisting of only an integer in the numerator and denominator. For example, pi is an irrational number while 1/3 is rational.