grayling

from The American Heritage® Dictionary of the English Language, 4th Edition

• 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License

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

from the GNU version of the Collaborative International Dictionary of English

• n. 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.
• n. 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.

from The Century Dictionary and Cyclopedia

• n. A fish of the family Salmonidæ and genus Thymallus.
• n. The dace.
• n. A common European butterfly, Hipparchia semele: so called from the gray under side of the wings.
• 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.
• n. An American agapetid butterfly, Cercyonis alope, which occurs in several well-marked varieties. See below.