From Longman Dictionary of Contemporary Englishbase metalˌbase ˈmetal noun [countable, uncountable] HCMa metal that is not very valuable, such as iron or lead
Examples from the Corpus
base metal• Gilded Finish Gilding is a process of overlaying a base metal with a very thin layer of gold.• Gold mineralisation is associated with earlier fluids; antimony and base metal sulphides with later fluids.• The area has potential for the discovery of base metal sulphides.• The transmutation of base metal to gold was the paradigm of this sacred task.• Mineralisation within the nodules consists of uranium, vanadium and iron oxides with base metal sulphides. 