Source : Webster's Revised Unabridged Dictionary (1913)

Sourwood \Sour"wood`\, n. (Bot.)
   The sorrel tree.

Source : WordNet®

sourwood
     n : deciduous shrubby tree of eastern North America having
         deeply fissured bark and sprays of small fragrant white
         flowers and sour-tasting leaves [syn: {sorrel tree}, {titi},
          {Oxydendrum arboreum}]