mannitol

n.
  1. (Chem.) A white crystalline hexose (HO.CH2.(CHOH)4.CH2.OH) of a sweet taste obtained from a so-called manna, the dried sap of the flowering ash (Fraxinus ornus); -- called also mannite, and hydroxy hexane. Cf. Dulcite. It is used in pharmacy as excipient and diluent for solids and liquids. It is also used as a food additive for anti-caking properties, or as a sweetener, and, illegally, to "cut" (dilute) illegal drugs such as cocaine or heroin.