boy·sen·ber·ry 
(boizən-bĕr′ē)
(boizən-bĕr′ē)n.
1. A usually prickly shrub that is a hybrid of a western North American blackberry (Rubus ursinus) and is cultivated for its edible, dark red to nearly black fruit.
2. The fruit of this plant.
[After Rudolph Boysen (1895-1950), American horticulturalist who first grew the hybrid.]