| Noun | 1. | genus Prosopium - whitefishes fish genus - any of various genus of fish Coregonidae, family Coregonidae - soft-finned fishes comprising the freshwater whitefishes; formerly included in the family Salmonidae Menominee whitefish, Prosopium cylindraceum, round whitefish - a whitefish with a bronze back; of northern North America and Siberia Prosopium williamsonii, Rocky Mountain whitefish - whitefish of the western United States and Canada |