JAZER, or JASER, (anc. geog.), a Levitical city in the territory of the Amorites beyond Jordan, 10 miles to the west, or rather south-west, of Philadelphia, and 15 miles from Eshebon; and therefore situated between Philadelphia and Eshebon, on the east border of the tribe of Gad, supposed to be the Jazorem of Josephus. In Jeremiah xlviii. mention is made of the sea of Jazer, that is a lake; taken either for an effusion or overflowing of the Arnon, or a lake thro' which it passes, or from which it takes its rise.