Man"nite (?), n. [Cf. F. mannite.] 1. (Chem.) A white crystalline substance of a sweet taste obtained from a so-called manna, the dried sap of the flowering ash (Fraxinus ornus); -- called also mannitol, and hydroxy hexane. Cf. Dulcite.

2. (Bot.) A sweet white efflorescence from dried fronds of kelp, especially from those of the Laminaria saccharina, or devil's apron.