adj 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. grayling ·adj 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.