noun.
A scombroid fish of the genus Orcynus, as O. thynnus.
the GNU version of the Collaborative International Dictionary of English
noun.
The chiefly British equivalent of tuna; any one of several species of large oceanic fishes belonging to the Mackerel family, especially the common or great tunny (Thunnus thynnus syn. Albacora thynnus, formerly Orcynus thynnus) native of the Mediterranean Sea and the Atlantic Ocean. It sometimes weighs a thousand pounds or more, and is extensively caught in the Mediterranean. On the American coast it is called horse mackerel. See Illust. of Horse mackerel, under horse.