arsenic trioxide ar·se·nict·rioxide uncommon noun 1. a white powdered poisonous trioxide of arsenic; used in manufacturing glass and as a pesticide (rat poison) and weed killer Synonymsarsenicarsenic trioxidearsenous anhydridearsenous oxide Related words Broader terms trioxide WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
