1. a grayish-white element having a metallic luster, vaporizing when heated, and forming poisonous compounds. Symbol: As; at. wt.: 74.92; at. no.: 33.
2. See arsenic trioxide.
3. a mineral, the native element, occurring in white or gray masses.
of or containing arsenic, esp. in the pentavalent state.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.