noun

1. any of various black-headed birds, esp. the scaup duck
2. a black-tipped plug of dried fatty matter in a pore of the skin
3. ☆ an infectious disease of the intestines and liver of turkeys, chickens, etc. caused by a protozoan (Histomonas meleagridis) and characterized by a dark, discolored comb
4. the parasitic larva of a freshwater mussel (family Unionidae) encysted in the gills, etc. of a fish