koan

koan
    n 1: a paradoxical anecdote or a riddle that has no solution;
         used in Zen Buddhism to show the inadequacy of logical
         reasoning
    

koan
 /koh'an/, n.

   A Zen teaching riddle. Classically, koans are attractive paradoxes to
   be meditated on; their purpose is to help one to enlightenment by
   temporarily jamming normal cognitive processing so that something more
   interesting can happen (this practice is associated with Rinzai Zen
   Buddhism). Defined here because hackers are very fond of the koan form
   and compose their own koans for humorous and/or enlightening effect.
   See Some AI Koans, {has the X nature}, {hacker humor}.