Blubber, in Physiology and Commerce, the fat which invests the bodies of all large cetaceous fishes, serving to furnish an oil. The blubber lies immediately under the skin, and over the muscular flesh. In the porpoise it is firm and full of fibres, and invests the body about an inch thick. In the whale its thickness is ordinarily 6 inches, but about the under lip it is found two or three feet thick.. The quantity yielded by one of these animals ordinarily amounts to forty, or fifty, sometimes to eighty or more hundred weight. Its use in trade and manufactures is to furnish train-oil, which it does by boiling down. Formerly this was performed ashore in the countries where the whales were caught, but lately the fishers do not go ashore; they bring the blubber home stowed in casks, and boil it down there. A machine expressly designed for expressing the oil from blubber is given under the word Oil.