noun
1. : tungsten trioxide
2. : any of various acids derived from tungsten trioxide ; especially : the simplest acid H 2 WO 4 analogous in composition to chromic acid and obtained as a yellow powder or as the white monohydrate H 2 WO 4 .H 2 O but known chiefly in the form of salts — compare heteropoly acid , metatungstic acid , phosphotungstic acid