Ta - a hard gray lustrous metallic element that is highly corrosion-resistant; occurs in niobite and fergusonite and tantalitemetal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc. fergusonite - a dark mineral consisting of oxides of yttrium and erbium and tantalum and other minerals tantalite - a mineral consisting of tantalum oxide of iron and manganese that occurs with niobite or in coarse granite; an ore of tantalum |