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 Simarubeæ, as Quassia amara, Picræna excelsa, and Simaruba amara. It is intensely bitter, and is used in medicine and sometimes as a substitute for hops in making beer.