The modern name for the rocky stone areas in the bed of the Nile that render navigation impossible. The First Cataract is situated just south of Elephantine, modern Aswan, and marks the original border between Egypt and Nubia. There are six numbered cataracts in the course of the Nile in Sudan before it divides into the White Nile and Blue Nile near Khartoum.
Historical Dictionary Of Ancient Egypt by Morris L. Bierbrier
Ancient Egypt. A Reference Guide. EdwART. 2011.