The Collaborative International Dictionary of English v.0.48:

Ravenala \Rav`e*na"la\ (r[a^]v`[-e]*n[aum]"l[.a]), n.
   [Malagasy.] (Bot.)
   A genus of plants related to the banana.
   [1913 Webster]

   Note: Ravenala Madagascariensis, the principal species, is
         an unbranched tree with immense oarlike leaves growing
         alternately from two sides of the stem. The sheathing
         bases of the leafstalks collect and retain rain water,
         which flows freely when they are pierced with a knife,
         whence the plant is called traveler's tree.
         [1913 Webster]

WordNet (r) 3.0 (2006):

ravenala
    n 1: giant treelike plant having edible nuts and leafstalks that
         yield a refreshing drink of clear watery sap; reputedly an
         emergency source of water for travelers [syn: traveler's
         tree, traveller's tree, ravenala, Ravenala
         madagascariensis]