mu

mu /moo/  The correct answer to the classic trick question
   "Have you stopped beating your wife yet?".  Assuming that you
   have no wife or you have never beaten your wife, the answer "yes"
   is wrong because it implies that you used to beat your wife and
   then stopped, but "no" is worse because it suggests that you have
   one and are still beating her.  According to various Discordians
   and Douglas Hofstadter the correct answer is usually "mu", a
   Japanese word alleged to mean "Your question cannot be answered
   because it depends on incorrect assumptions".  Hackers tend to be
   sensitive to logical inadequacies in language, and many have
   adopted this suggestion with enthusiasm.  The word `mu' is
   actually from Chinese, meaning `nothing'; it is used in
   mainstream Japanese in that sense, but native speakers do not
   recognize the Discordian question-denying use.  It almost certainly
   derives from overgeneralization of the answer in the following
   well-known Rinzei Zen teaching riddle:

     A monk asked Joshu, "Does a dog have the Buddha nature?"  Joshu
     retorted, "Mu!"

   See also {has the X nature}, {AI Koans}, and Douglas
   Hofstadter's "G"odel, Escher, Bach: An Eternal Golden Braid"
   (pointer in the {Bibliography} in Appendix C.