Definition of cinchonas:
(n) :
The bark of these plants, which yield quinine and other alkaloids useful in reducing fevers and particularly in combatting malaria.
(n) :
(medicine) Any medicine chiefly composed of the prepared bark of these plants.
(n) :
A tree or shrub of the genus Cinchona, native to the Andes in South America but since widely cultivated in Indonesia and India as well for its medicinal bark.