[¦səl¦fyu̇r·ik ′ī·ə‚dīn] (inorganic chemistry) I2S2 A gray-black brittle mass with an iodine aroma and a metallic luster, insoluble in water, soluble in carbon disulfide; used in medicine. Also known as iodine bisulfide; iodine disulfide; sulfur iodide.