MISGAB (mĭs'găb, Heb. ha-misgāv, a lofty place). A town in the high hills of Moab, possibly another name for Moab’s capital (Jer.48.1). Thus the NIV rendering, “the stronghold.”
MISGAB mĭs’ găb (הַמִּשְׂגָּ֖ב, ha-misgab, the height). The KJV, ASV rendering of the Heb. word (Jer 48:1 RSV, “the fortress”).
International Standard Bible Encyclopedia (1915)
Named with Nebo and Kiriathaim in the denunciation of doom against Moab (Jer 48:1). No trace of any name resembling this has been found. Possibly we should take it, not as a place-name, but as an appellation of some strong fortress, perhaps of Kir-moab itself. The term is elsewhere translated "high fortress" (Isa 25:12, etc.).