- A bitter, colorless, amorphous powder or crystalline alkaloid, C<sub>20</sub>H<sub>24</sub>N<sub>2</sub>O<sub>2</sub><strong>·</strong>3H<sub>2</sub>O, derived from certain cinchona barks and used in medicine to treat malaria.
- Any of various compounds or salts of quinine.
- A very important vegetable alkali (C<sub>20</sub>H<sub>24</sub>N<sub>2</sub>O<sub>2</sub>), obtained from the bark of several trees of the genus <em>Cinchona.</em>
- An alkaloid extracted from the bark of several species of cinchona (esp. <spn>Cinchona Calisaya</spn>) as a bitter white crystalline substance, C20H24N2O2. Hence, by extension (Med.), any of the salts of this alkaloid, as the acetate, chloride, sulphate, etc., employed as a febrifuge or antiperiodic. Called also <altname>quinia</altname>, <altname>quinina</altname>, etc.
- A <xref>bitter</xref> <xref>colourless</xref> <xref>powder</xref>, an <xref>alkaloid</xref> derived from <xref>cinchona</xref> <xref>bark</xref>, used to treat <xref>malaria</xref> and as an ingredient of <xref>tonic water</xref>.
- a bitter alkaloid extracted from chinchona bark; used in malaria therapy