| Noun | 1. | samarium - a grey lustrous metallic element of the rare earth group; is used in special alloys; occurs in monazite and bastnasitemetal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc. bastnaesite, bastnasite - a yellow-to-brown mineral that is a source of rare earth elements monazite - a reddish-brown mineral containing rare earth metals; an important source of thorium and cerium |