The term DECAYING METAL can be summarized as a metal that is undergoing a process of decay, such as corrosion or oxidation. The crossword solution for this term is RADIUM, which is a radioactive element that was discovered by Marie and Pierre Curie in 1898. Radium is known for its intense radioactivity and has been used in medical treatments, but it is also highly toxic and has been linked to various health issues.