Pronunciation: (blak'hed"),[key] —n. 1. a small, black-tipped, fatty mass in a skin follicle, esp. of the face; comedo.
2. any of several birds having a black head, as the greater scaup, Aythya marila. 3. Also called enterohepatitis.Vet. Pathol.a malignant, infectious disease of turkeys, chickens, and many wild birds, caused by a protozoan parasite, Histomonas meleagridas, attacking esp. the intestines and liver, and often characterized by a darkening of the skin on the head.