Noun | 1. | Didelphidae - opossums mammal family - a family of mammals Marsupialia, order Marsupialia - coextensive with the subclass Metatheria possum, opossum - nocturnal arboreal marsupial having a naked prehensile tail found from southern North America to northern South America Didelphis, genus Didelphis - type genus of the family Didelphidae |