I. ˈ ̷ ̷ˌ ̷ ̷ noun
1. : any of various birds with more or less black about the head ; especially : scaup duck
2. : comedo
3. : a destructive disease of turkeys and in a milder form of chickens and other related birds caused by a protozoan ( Histomonas meleagridis ) that invades the intestinal ceca and liver causing tissue destruction and necrosis and intense systemic reaction and that is commonly transmitted from bird to bird by fecal contamination but maintained in nature by intermediate stages developed in the cecal worm ( Heterakis gallinae ) from which it may pass directly to the bird — called also enterohepatitis, infectious enterohepatitis
4. : a glochidium larva of a freshwater clam or mussel attached to the skin or gills of any of several freshwater fishes and with the cells of its host growing around it in a blackish mass
II. adjective
: having a black head