Noun | 1. | ![]() fish genus - any of various genus of fish family Scombridae, Scombridae - marine food fishes: mackerels; chub mackerels; tuna tunny, tuna - any very large marine food and game fish of the genus Thunnus; related to mackerel; chiefly of warm waters horse mackerel, Thunnus thynnus, bluefin, bluefin tuna - largest tuna; to 1500 pounds; of mostly temperate seas: feed in polar regions but breed in tropics |