a. Chem. [f. TANTALUM + -OUS.] Applied to compounds containing a greater proportion of tantalum than those called tantalic, as tantalous oxide, tantalum dioxide, TaO2.
1868. Watts, Dict. Chem., V. 665. Dioxide of Tantalum, or Tantalous Oxide … is a dark-grey mass, which scratches glass, and acquires metallic lustre by burnishing.
