Definition of blackhead
1
:a small plug of darkened sebum and dead skin cells that fills a pore of the skin especially on the face — called also
comedo, open comedo; compare whitehead
2
:a destructive disease of turkeys and related birds caused by a protozoan (Histomonas meleagridis) that invades the intestinal ceca and liver
3
:a larval clam or mussel attached to the skin or gills of a freshwater fish
