'Possum' definitions:

Definition of 'possum'

noun

Nocturnal arboreal marsupial having a naked prehensile tail found from southern North America to northern South America [syn: opossum, possum]

noun

Small furry Australian arboreal marsupials having long usually prehensile tails [syn: phalanger, opossum, possum]

From: GCIDE

Possum \Pos"sum\, n. [Shortened from opossum.] (Zool.) An opossum. [Colloq. U. S.] [1913 Webster]
To play possum, To act possum, to feign ignorance, indifference or inattention, with the intent to deceive; to dissemble; -- in allusion to the habit of the opossum, which feigns death when attacked or alarmed. [1913 Webster]