Any of an Old World group of freshwater fishes of the carp family, especially the species G. gobio found in Europe and northern Asia on the gravel bottoms of streams. It is olive-brown, spotted with black, and up to 20 cm/8 in long, with a distinctive barbel (sensory bristle, or 'whisker') at each side of the mouth. (Genus Gobio, family Cyprinidae.)