Blubber is the thick layer of fat beneath the skin of whales, seals, walruses, and other marine mammals. This fat works like a built-in winter coat, keeping these animals warm even in freezing Arctic waters. A whale's blubber can be over a foot thick, creating such effective insulation that the whale stays comfortable in water cold enough to give you hypothermia in minutes.

Blubber also stores energy, like a portable pantry. When food becomes scarce, these animals can survive by burning the fat they've stored in their blubber. Gray whales, for example, eat enormous amounts during summer feeding, building up their blubber so they can travel thousands of miles during winter migration without eating much at all.

Historically, humans hunted whales for their blubber, which could be melted down into oil for lamps, candles, and machinery before petroleum was widely used. This whaling industry nearly drove many whale species to extinction before people recognized how devastating it was and created protections.

The word blubber is also used as a verb meaning to cry noisily and uncontrollably, with tears and sobbing. A child might blubber after scraping their knee badly, or someone might start blubbering when overwhelmed with emotion. This meaning probably comes from how your face and lips might puff up and look swollen when you cry hard.