- A tropical American shrub or small tree <em>(Quassia amara)</em> having bright scarlet flowers and yielding a fine-grained, yellowish-white wood.
- The wood of this plant.
- A bitter substance obtained from the wood of this plant or related plants in the family Simaroubaceae, used in medicine and formerly as an insecticide.
- Any of several <xref>tropic</xref> <xref>trees</xref>, of the genus Quassia, having scarlet flowers
- The bitter substance <xref>quassin</xref> extracted from its bark