- arsenic, As, atomic number 33 - 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
--1 is a kind of chemical element, element
--1 is a substance ofherbicide, weedkiller, weed killer; insecticide, insect powder; arsenopyrite, mispickel; orpiment; realgar - arsenic, arsenic trioxide, arsenous anhydride, arsenous oxide - a white powdered poisonous trioxide of arsenic; used in manufacturing glass and as a pesticide and weed killer
--2 is a kind of trioxide