Source : Webster's Revised Unabridged Dictionary (1913)

Manna \Man"na\, n. [L., fr. Gr. ?, Heb. m[=a]n; cf. Ar. mann,
   properly, gift (of heaven).]
   1. (Script.) The food supplied to the Israelites in their
      journey through the wilderness of Arabia; hence, divinely
      supplied food. --Ex. xvi. 15.

   2. (Bot.) A name given to lichens of the genus {Lecanora},
      sometimes blown into heaps in the deserts of Arabia and
      Africa, and gathered and used as food.

   3. (Bot. & Med.) A sweetish exudation in the form of pale
      yellow friable flakes, coming from several trees and
      shrubs and used in medicine as a gentle laxative, as the
      secretion of {Fraxinus Ornus}, and {F. rotundifolia}, the
      manna ashes of Southern Europe.

   Note: {Persian manna} is the secretion of the camel's thorn
         (see {Camel's thorn}, under {Camel}); {Tamarisk manna},
         that of the {Tamarisk mannifera}, a shrub of Western
         Asia; {Australian, manna}, that of certain species of
         eucalyptus; {Brian[,c]on manna}, that of the European
         larch.

   {Manna grass} (Bot.), a name of several tall slender grasses
      of the genus {Glyceria}. they have long loose panicles,
      and grow in moist places. {Nerved manna grass} is
      {Glyceria nervata}, and {Floating manna grass} is {G.
      flu}.

   {Manna insect} (Zo["o]l), a scale insect ({Gossyparia
      mannipara}), which causes the exudation of manna from the
      Tamarisk tree in Arabia.

Source : WordNet®

Fraxinus ornus
     n : southern Mediterranean ash having fragrant white flowers in
         dense panicles and yielding manna [syn: {manna ash}, {flowering
         ash}]