Source : Webster's Revised Unabridged Dictionary (1913)

Goa powder \Go"a pow"der\ [So called from Goa, on the Malabar
   coast, whither it was shipped from Portugal.]
   A bitter powder (also called {araroba}) found in the
   interspaces of the wood of a Brazilian tree ({Andira
   araroba}) and used as a medicine. It is the material from
   which chrysarobin is obtained.

Source : WordNet®

Goa powder
     n : a bitter yellow powder used to treat skin diseases [syn: {araroba},
          {chrysarobin}]