a white powdered poisonous trioxide of arsenic; used in manufacturing glass and as a pesticide (rat poison) and weed killer

[ Syn: arsenic trioxide , arsenous anhydride , arsenous oxide , white arsenic , ratsbane ]

a very poisonous metallic element that has three allotropic forms; arsenic and arsenic compounds are used as herbicides and insecticides and various alloys; found in arsenopyrite and orpiment and realgar

[ Syn: as , atomic number 33 ]