Pronunciation: (fē"nu-thī'u-zēn", -zin),[key] —n. 1. Chem.a grayish-green to greenish-yellow, crystalline, water-insoluble solid, C12H9NS, used chiefly as an insecticide and vermifuge, and in the synthesis of pharmaceuticals.
2. Pharm.any of a class of medications used principally to treat psychotic symptoms, as delusions or hallucinations, and excessive excitability.