whale oil, oil extracted from the blubber and other parts of certain species of whales. It varies in composition, color, and the degree of fishy odor according to the method and extent of refining. Formerly widely used as an illuminant, it was superseded by petroleum products. It is used today in soapmaking, as a leather dressing, and as a lubricant. Some is hydrogenated to form edible fats. The term is also sometimes used to include sperm oil.