noun
: a white or transparent glassy extremely poisonous compound As 2 O 3 or As 4 O 6 that occurs naturally as arsenolite and claudetite, that is obtained usually from the flue dusts from smelters roasting arsenic-containing ores, and that is used especially as a decolorizing agent chiefly in making insecticides, weed killers, pigments, and glass — called also arsenious oxide, white arsenic