Lewis & Short

Mōab, f. indecl., the mountainous region on the eastern coast of the Dead Sea, extending from Zoar to the river Arnon, Vulg. Gen. 36, 35; 48, 15 and 20, etc.
Hence,

  1. A. Mōăbītēs, ae, m., an inhabitant of Moab, a Moabite, Vulg. 1 Chron. 11, 46.
    Plur.: Moabitae (= Μωαβῖται), the Moabites, Vulg. Gen. 19, 37 et saep.
  2. B. Mōăbītis, tĭdis, f. (Μωαβῖτις).
    1. 1. Moabite (sc. regio), the land of the Moabites, Moab, Vulg. Ruth, 1, 1.
    2. 2. Subst., a Moabitish woman, Vulg. Ruth, 1, 22.