"arsenics" in the noun sense
1. arsenic, arsenic trioxide, arsenous anhydride, arsenous oxide, white arsenic, ratsbane
a white powdered poisonous trioxide of arsenic used in manufacturing glass and as a pesticide (rat poison) and weed killer
2. 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
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