Pronunciation: (u-pos'um, pos'um),[key] —n., —pl.-sums,(esp. collectively)-sum. 1. 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.
2. any of various animals of related genera.Cf. possum.