Hebrew, a bath or baptism done in full immersion to achieve ritual purity. A mikveh should include some portion from a natural source of water.
See Law of the Lord 11; 2 Nephi 13:7 RAV, 31:15 OPV; Mosiah 11:129 RAV, 26:22a OPV; Matthew 3:11; John 3:5-7;