Definition of "arsenic" []

• A highly poisonous metallic element having three allotropic forms, yellow, black, and gray, of which the brittle, crystalline gray is the most common. Arsenic and its compounds are used in insecticides, weed killers, solid-state doping agents, and various alloys. Atomic number 33; atomic weight 74.922; valence 3, 5. Gray arsenic melts at 817°C (at 28 atm pressure), sublimes at 613°C, and has a specific gravity of 5.73. See Table at element. (noun)
• Arsenic trioxide. (noun)
• Of or containing arsenic, especially with valence 5. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The name arsenic comes from the Greek word arsenikon, which means orpiment."
• "Reed believes her son has reason to worry because "arsenic is poison.""
• "However, the regulator, usually a lawyer, knows that arsenic is a poison."