ORONOKO, or ORINOCO, a large river of South America, which rises in Spanish Guiana, about 5° N. Lat. Its course has a spiral form, running first east, then south, then west, then north, and at last east again. It falls into the Atlantic ocean in N. Lat. 9° after a course of 1400 miles, during which it is joined by several large rivers, which flow eastward from the Andes.