n. & adj.
n. 1 a non-scientific name for arsenic trioxide, a highly poisonous white powdery substance used in weed-killers, rat poison, etc. 2 Chem. a brittle semi-metallic element, used in semiconductors and alloys. °Symb.: As.
adj. 1 of or concerning arsenic. 2 Chem. containing arsenic with a valency of five. red arsenic = REALGAR. white arsenic = sense 1. arsenious adj.
[ ME f. OF f. L arsenicum f. Gk arsenikon yellow orpiment, identified with arsenikos male, but in fact f. Arab. al-zarnik f. al the + zarnik orpiment f. Pers. f. zar gold ]