Any of various marine mammals of the order Cetacea, having the general shape of a fish with forelimbs modified to form flippers, a tail with horizontal flukes, and one or two blowholes for breathing, especially one of the very large species as distinguished from the smaller dolphins and porpoises. Informal An impressive example: a whale of a story. To engage in the hunting of whales. To strike or hit repeatedly and forcefully; thrash. To attack vehemently: The poet whaled away at the critics.