Rhinoceros is primarily a free form surface modeler that utilizes the NURBS mathematical model. Rhinoceros' application architecture and open SDK makes it modular and enables the user to customize the interface and create custom commands and menus.
Noun. 1. exigency-a pressing or urgent situation; the health-care exigency. crisis-an unstable situation of extreme danger or difficulty; they went bankrupt during the economic crisis.
Extensibility(noun) the quality of being extensible; the capacity of being extended; as, the extensibility of a fiber, or of a plate of metal.