grayling

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of several freshwater food and game fishes of the genus Thymallus of the Northern Hemisphere, having a small mouth and large dorsal fin.

Century Dictionary and Cyclopedia

1. n. A fish of the family Salmonidæ and genus Thymallus. There are several species, intermediate between the whitefish and the trout, chiefly characterized by the greater development of the dorsal fin, which is long and contains 20 to 24 rays; this flu is also brightly party-colored. They inhabit clear cold streams of northern countries. The common grayling of Europe is Thymallus vulgaris; related species are the American or Alaskan grayling, T. signifer, and the Michigan grayling, T. ontariensis.
2. n. The dace.
3. n. A common European butterfly, Hipparchia semele: so called from the gray under side of the wings.
4. n. In Australia, Prototroctes muræna, of the family Hoplochitonidæ, a fish which remotely resembles the English grayling. Also called cucumber-fish, cucumber-mullet, fresh-water herring, and Yarra herring.
5. n. An American agapetid butterfly, Cercyonis alope, which occurs in several well-marked varieties. See below.

Wiktionary

1. n. Any freshwater fish of the genus Thymallus or specifically Thymallus thymallus, of the salmon family, having a large dorsal fin.
2. n. A species of butterfly, Hipparchia semele, of the family Nymphalidae.

GNU Webster's 1913

1. n. (Zoöl.) A European fish (Thymallus vulgaris), allied to the trout, but having a very broad dorsal fin; -- called also umber. It inhabits cold mountain streams, and is valued as a game fish.
2. n. (Zoöl.) An American fish of the genus Thymallus, having similar habits to the above; one species (T. Ontariensis), inhabits several streams in Michigan; another (T. montanus), is found in the Yellowstone region.