n a hard grey lustrous metallic element that is highly resistant to corrosion; occurs in niobite and fergusonite and tantalite
abbr. 旅游者援助协会（Traveler ' s Aid Society）；电话接听系统（Telephone Answering System）；实际空速（True Airspeed）；印字电报机自动换接（Teleprinter Automatic Switching）