The Collaborative International Dictionary of English v.0.48:

Fraxinus \Frax"i*nus\, prop. n. [L., the ash tree.] (Bot.)
   A genus of deciduous forest trees, found in the north
   temperate zone, and including the true ash trees.
   [1913 Webster]

   Note: Fraxinus excelsior is the European ash; Fraxinus
         Americana, the white ash; Fraxinus sambucifolia, the
         black ash or water ash.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ash \Ash\ ([a^]sh), n. [OE. asch, esh, AS. [ae]sc; akin to OHG.
   asc, Sw. & Dan. ask, Icel. askr, D. esch, G. esche.]
   1. (Bot.) A genus of trees of the Olive family, having
      opposite pinnate leaves, many of the species furnishing
      valuable timber, as the European ash (Fraxinus
      excelsior) and the white ash (Fraxinus Americana).
      [1913 Webster]

   Prickly ash (Zanthoxylum Americanum) and Poison ash
      (Rhus venenata) are shrubs of different families,
      somewhat resembling the true ashes in their foliage.

   Mountain ash. See Roman tree, and under Mountain.
      [1913 Webster]

   2. The tough, elastic wood of the ash tree.
      [1913 Webster]

   Note: Ash is used adjectively, or as the first part of a
         compound term; as, ash bud, ash wood, ash tree, etc.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Fraxinus Americana
    n 1: spreading American ash with leaves pale green or silvery
         beneath and having hard brownish wood [syn: white ash,
         Fraxinus Americana]