Members of the infraclass Metatheria of the class Mammalia. The young are born at a relatively less developed stage than those of placental mammals; after birth, the young animal attaches to a mammary gland in the pouch, where it continues to grow and develop.
Mammals that give birth to young at a very immature stage, e.g. kangaroos. While many marsupials have pouches, not all do.
Any of an order (Marsupialia) of mammals comprising kangaroos, wombats, bandicoots, opossums, and related animals that usually have a pouch on the abdomen of the female which covers the teats and serves to carry the young.