Barium: 1. A metallic element belonging to the alkaline earths with an atomic number of 56 and an atomic weight of 137.34. The symbol for barium is Ba.
2. In medicine, refers to a chalky solution of barium used to coat the inside of organs, such as the stomach or intestines so that they will show up on an x-ray.
See also: Barium enema; Barium swallow.
