1Any of the trees of the genus Cinchona (family Rubiaceae), which yield quinine.

2Australian. Any of several Australian trees suggesting the presence of quinine by the bitterness of their bark, leaves, fruit, etc., especially those of the genus Petalostigma (family Euphorbiaceae), which have bitter fruits, and the bitter bark, Alstonia constricta (family Apocynaceae).

3South African. Any of several southern African trees of the family Apocynaceae; especially Rauvolfia caffra, the bark of which is used in traditional medicine for its supposed quinine-like properties.