Definition of "koan"

koan

/ˈkəʊ.ɑːn/

noun
plural koans
1. (Zen Buddhism) A story about a Zen master and his student, sometimes like a riddle, other times like a fable, which has become an object of Zen study, and which, when meditated upon, may unlock mechanisms in the Zen student’s mind leading to satori.
  Quotations
  Zen, with its absurdist koan, laughs at life much the way the Marx brothers did. What exactly can you make of a philosophical system whose teacher answers the question, "How do you see things so clearly?" with the seeming one-liner, "I close my eyes"?
  1977, Thomas Hoover, chapter 1, in Zen Culture‎
2. A riddle with no solution, used to provoke reflection on the inadequacy of logical reasoning, and to lead to enlightenment.
  Quotations
  Gibberish. Or else a koan that Achtfaden isn’t equipped to master, a transcendent puzzle that could lead him to some moment of light.
  1973, Thomas Pynchon, Gravity’s Rainbow
  As always the koan “Why, Why am I here, why here” begins in her head, but she beats it back like a housewife with a broom.
  2001, Joyce Carol Oates, Middle Age, paperback edition, Fourth Estate, page 303
3. A therapy technique used by Traditional Chinese medicinal physicians or medical practitioners to break a presenting patients habitual pattern of thinking that has been diagnosed as the primary cause of a illness or disease.