Real Dictionary

opossum
variable noun: An opossum is a small animal that lives in America. It carries its young in a pouch on its body, and has thick fur and a long tail.

opossum in American English
any of various families (esp. Didelphidae) of marsupials; esp., any of a small, omnivorous, tree-dwelling American species (Didelphis marsupialis) with a ratlike, prehensile tail, that is active at night and becomes motionless when endangered
noun: a prehensile-tailed marsupial, Didelphis virginiana, of the eastern U.S., the female having an abdominal pouch in which its young are carried: noted for the habit of feigning death when in danger

opossum in British English
noun: any thick-furred marsupial, esp Didelphis marsupialis ( common opossum), of the family Didelphidae of S North, Central, and South America, having an elongated snout and a hairless prehensile tail