CIDE DICTIONARY
possum, n. [Shortened from opossum.].
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.
THESAURUS
possum
Cape polecat, ape, bar, bear, cavy, chimp, chimpanzee, coon, ferret, foumart, glutton, groundhog, guinea pig, hedgehog, monk, monkey, mousehound, opossum, polecat, porcupine, prairie dog, quill pig, raccoon, skunk, weasel, whistle-pig, wolverine, woodchuck, zoril