| Noun | 1. | vanadium - a soft silvery white toxic metallic element used in steel alloys; it occurs in several complex minerals including carnotite and vanadinitemetal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc. carnotite - a yellow radioactive mineral; an ore of uranium and radium and vanadium vanadinite - a mineral consisting of chloride and vanadate of lead; a source of vanadium |