<p><strong>noun</strong></p><ul><li>a grayish-white element having a metallic luster, vaporizing when heated, and forming poisonous compounds.</li><li>arsenic trioxide.</li><li>a mineral, the native element, occurring in white or gray masses.</li></ul><p><strong>adjective</strong></p><ul><li>of or containing arsenic, especially in the pentavalent state.</li></ul>