While waiting in a typical afternoon's long line at the local dump, I read the list of items that they won't accept and saw the unfamiliar term "TENORM". While my 280-pound load of scrap wood and ceramic tile was probably OK, I had to know, just to be cautious.
TENORM stands for "Technologically Enhanced Naturally Occurring Radioactive Materials" and occurs when naturally occurring radioactive materials, which are generally safe, are concentrated and present a real threat. This occurs in a variety of manufacturing processes, often the result of wastes and residuals. Loads more information at this EPA link.