ARSENIC

I. noun see: yellow Date: 14th century a trivalent and pentavalent metalloid poisonous element that is commonly metallic steel gray, crystalline, and brittle and is used especially in wood preservatives, alloys, and semiconductors, a poisonous trioxide As 2 O 3 or As 4 O 6 of ~ used especially as an insecticide or weed killer, II. adjective Date: 1801 of, relating to, or containing ~ especially with a valence of five