- any of various black-headed birds, esp. the scaup duck
- a black-tipped plug of dried fatty matter in a pore of the skin
- ⌂ 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
- the parasitic larva of a freshwater mussel (family Unionidae) encysted in the gills, etc. of a fish
- A skin lesion consisting of a hair follicle that is occluded with sebum and keratin, appearing black at the surface.
- An infectious disease of turkeys and some wildfowl that is caused by a protozoan (Histomonas meleagridis) and results in lesions of the intestine and liver. Also called enterohepatitis, histomoniasis, infectious enterohepatitis.
- Any of various birds, such as the scaup, with dark head markings.
- (medicine) A comedo, a skin blemish, a type of acne vulgaris, where a pore becomes clogged with a dark, hard, cheesy keratin-filled substance forming a hard black "head" on the skin's surface.
- A form of histomoniasis in poultry, characterized by cyanotic discoloration on the bird's head.
- A scaup: a kind of duck.