crux \KRUHKS\, noun; plural cruxes, also cruces \KROO-seez\: 1. The basic, central, or critical point or feature. 2. Anything that is very puzzling or difficult to explain or solve. Ah, and now it was out of the bag, O'Kane thought, the crux of the matter. -- T. Coraghessan Boyle, Riven Rock The... Sign in to see full entry.