co·nun·drum /kəˈnʌndrəm/
  謎,難題,謎樣的人
  Co·nun·drum n.
  1. A kind of riddle based upon some fanciful or fantastic resemblance between things quite unlike; a puzzling question, of which the answer is or involves a pun.
     Or pun ambiguous, or conundrum quaint.   --J. Philips.
  2. A question to which only a conjectural answer can be made.
     Do you think life is long enough to let me speculate on conundrums like that?   --W. Black.
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  conundrum
       n : a difficult problem [syn: riddle, enigma, brain-teaser]