The Collaborative International Dictionary of English v.0.48:

Fustic \Fus"tic\, n. [F. fustoc, Sp. fustoc. Cf. Fustet.]
   The wood of the Maclura tinctoria, a tree growing in the
   West Indies, used in dyeing yellow; -- called also old
   fustic. [Written also fustoc.]
   [1913 Webster]

   Note: Other kinds of yellow wood are often called fustic; as
         that of species of Xanthoxylum, and especially the
         Rhus Cotinus, which is sometimes called young fustic
         to distinguish it from the Maclura. See Fustet.
         [1913 Webster]