black dolphin
noun
1(More fully black dolphin fly) a black aphid, a blackfly; specifically the bean aphid, Aphis fabae; (now rare ).
2Any of several marine dolphins (family Delphinidae) with black skin; especially the long-finned pilot whale, Globicephala melas, and the Chilean dolphin, Cephalorhynchus eutropia.
Origin
Mid 18th century; earliest use found in William Ellis (c1700–1758), agriculturist and writer.