any one of numerous species of fishes belonging to salmo, salvelinus, and allied genera of the family salmonidae. they are highly esteemed as game fishes and for the quality of their flesh. all the species breed in fresh water, but after spawning many of them descend to the sea if they have an opportunity.-any one of several species of marine fishes more or less resembling a trout in appearance or habits, but not belonging to the same family, especially the california rock trouts, the common squeteague, and the southern, or spotted, squeteague; -- called also salt-water trout, sea trout, shad trout, and gray trout. see squeteague, and rock trout under rock.