Cush is named once in the Book of Mormon, in Nephi1’s quotation of Isaiah1 (2 Nephi 21:11, paralleling Isaiah 11:11). It appears in a list of the lands from which the Lord will recover the remnant of his people a second time: Assyria, Egypt, Pathros, Cush, Elam, Shinar, Hamath, and the islands of the sea (2 Nephi 21:11). The passage describes the house of Israel as scattered among these regions and gathered from them in a future day.
The record gives no further detail and does not fix the location. Cush is typically identified with the region south of Egypt, corresponding to modern Ethiopia, the same identification found in the Bible, where Cush is often rendered as Ethiopia.