The Collaborative International Dictionary of English v.0.48:

Gamboge \Gam*boge"\, n.
   A concrete juice, or gum resin, produced by several species
   of trees in Siam, Ceylon, and Malabar. It is brought in
   masses, or cylindrical rolls, from Cambodia, or Cambogia, --
   whence its name. The best kind is of a dense, compact
   texture, and of a beatiful reddish yellow. Taken internally,
   it is a strong and harsh cathartic and emetic. [Written also
   camboge.]
   [1913 Webster]

   Note: There are several kinds of gamboge, but all are derived
         from species of Garcinia, a genus of trees of the
         order Guttifer[ae]. The best Siam gamboge is thought
         to come from Garcinia Hanburii. Ceylon gamboge is
         from G. Morella. G. pictoria, of Western India,
         yields gamboge, and also a kind of oil called gamboge
         butter. Gambogian

WordNet (r) 3.0 (2006):

gamboge
    n 1: a gum resin used as a yellow pigment and a purgative
    2: a strong yellow color [syn: gamboge, lemon, lemon
       yellow, maize]