Milk, liquid secreted by the mammary glands of female mammals to nourish their young for a period beginning immediately after birth. The milk of domesticated animals is also an important food source for humans, either as a fresh fluid or processed into a number of dairy products such as butter and cheese.

the white liquid produced by cows, goats, and sheep and used by humans as a drink or for making butter, cheese, etc.: a glass / carton of milk. cow's/goat's milk. skimmed / pasteurized milk.