Definition of "koan"
noun:
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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.
from Wiktionary, Creative Commons Attribution/Share-Alike License -
A riddle with no solution, used to provoke reflection on the inadequacy of logical reasoning, and to lead to enlightenment.
from Wiktionary, Creative Commons Attribution/Share-Alike License
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