Definition from Wiktionary, the free dictionary
blackhead (plural blackheads)
- (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.