Arsenic/ˈɑːrsnɪk/ Definition 1 of 3Pro Tip 1/2Poison Association Arsenic is often associated with murder mysteries due to its toxic nature. The detective suspected the use of arsenic in the old murder case. Pro Tip 2/2Avoid Casual Use Avoid using 'arsenic' in casual contexts due to its dangerous implications. I wouldn't joke about arsenic in my drink; it's serious.