I. ar·se·nic ˈärs-nik, ˈär-sə- noun
Etymology: Middle English arsenik orpiment, from Anglo-French & Latin; Anglo-French, from Latin arsenicum, from Greek arsenikon, arrhenikon, from Syriac zarnīg, of Iranian origin; akin to Avestan zaranya gold, Sanskrit hari yellowish — more at yellow
Date: 14th century
1. : 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 — see element table
2. : a poisonous trioxide As 2 O 3 or As 4 O 6 of arsenic used especially as an insecticide or weed killer — called also arsenic trioxide
II. ar·sen·ic är-ˈse-nik adjective
Date: 1801
: of, relating to, or containing arsenic especially with a valence of five