The waste, probably some high waste land to the south of the
Dead Sea (Num. 21:20; 23:28; 1 Sam. 23:19, 24); or rather not a
proper name at all, but simply “the waste” or “wilderness,” the
district on which the plateau of Ziph (q.v.) looks down.
Smith's Dictionary
(a wilderness), a name which occurs in (Numbers 21:20) and Numb 23:28 In designating the position of Pisgah and Peor; both described as “facing the Jeshimon.” Perhaps the dreary, barren waste of hills lying immediately on the west of the Dead Sea.