Source : Webster's Revised Unabridged Dictionary (1913)

Quassia \Quas"si*a\, n. [NL. From the name of a negro, Quassy,
   or Quash, who prescribed this article as a specific.]
   The wood of several tropical American trees of the order
   {Simarube[ae]}, as {Quassia amara}, {Picr[ae]na excelsa}, and
   {Simaruba amara}. It is intensely bitter, and is used in
   medicine and sometimes as a substitute for hops in making
   beer.

Bitterwood \Bit"ter*wood`\, n.
   A West Indian tree ({Picr[ae]na excelsa}) from the wood of
   which the bitter drug Jamaica quassia is obtained.