The Collaborative International Dictionary of English v.0.48:

Tolu \To*lu"\, n.
   A fragrant balsam said to have been first brought from
   Santiago de Tolu, in New Granada. See Balsam of Tolu, under
   Balsam.
   [1913 Webster]

   Tolu tree (Bot.), a large tree (Myroxylon toluiferum),
      the wood of which is red in the center, and has an
      aromatic rose odor. It affords the balsam called tolu.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tolu
    n 1: aromatic yellowish brown balsam from the tolu balsam tree
         used especially in cough syrups [syn: tolu, balsam of
         tolu, tolu balsam]