The light spongy pulp of the fruit of the bitter cucumber (
Citrullus colocynthis, 
or  Cucumis colocynthis), an Asiatic plant allied to the watermelon; coloquintida. It comes in white balls, is intensely bitter, and a powerful cathartic. Called also 
bitter apple, 
bitter cucumber, 
bitter gourd.		                                        		                                         [
1913 Webster]