Conundrum /(?)/

Co·nun·drum

Conundrum

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?