any viviparous, nonplacental mammal of the order Marsupialia, comprising the opossums, kangaroos, wombats, and bandicoots, the females of most species having a marsupium containing the mammary glands and serving as a receptacle for the young.
any vertebrate of the class Mammalia, having the body more or less covered with hair, nourishing the young with milk from the mammary glands, and, with the exception of the egg-laying monotremes, giving birth to live young.
