Source : Webster's Revised Unabridged Dictionary (1913)

Crux \Crux\ (kr[u^]ks), n.; pl. E. {Cruxes} (-[e^]z), L.
   {Cruces} (kr[udd]"s[=e]z). [L., cross, torture, trouble.]
   Anything that is very puzzling or difficult to explain. --Dr.
   Sheridan.

         The perpetual crux of New Testament chronologists.
                                                  --Strauss.