The Collaborative International Dictionary of English v.0.48:

Corkwood \Cork"wood`\ (k[^o]rk"w[oo^]d`), n.
   1. The wood of the cork oak. [Obs.]
      [Webster 1913 Suppl.]

   2. Any one of several trees or shrubs having light or corky
      wood; esp.:
      (a) In the United States, the tree Leitneria floridana,
          a very small deciduous dioecious tree or shrub of damp
          habitats in the southeastern US having extremely light
          wood; -- called also the corkwood tree.
      (b) In the West Indies: (1) Either of the cotton trees
          Ochroma lagopus and Pariti tiliaceum. (2) The tree
          producing the aligator apple. (3) The blolly.
          [Webster 1913 Suppl. + WordNet 1.5]

WordNet (r) 3.0 (2006):

corkwood tree
    n 1: very small deciduous dioecious tree or shrub of damp
         habitats in southeastern United States having extremely
         light wood [syn: corkwood, corkwood tree, Leitneria
         floridana]