1. A form of pneumoconiosis due to the presence of iron dust.
2. Discoloration of any part by desposition of a pigment containing iron; usually called hemosiderosis.
3. An excess of iron in the circulating blood.
4. Degeneration of the retina, lens, and uvea as a result of the deposition of intraocular iron.
The definition information for siderosis is provided by Stedman's. You can search our medical dictionary here.