possum

Concise Oxford English Dictionary © 2008 Oxford University Press:
possum/ˈpɒsəm/

▶noun

• 1 a tree-dwelling Australasian marsupial, typically with a prehensile tail. [Many species, especially in the family Petauridae.]

• 2 N. Amer. informal an opossum.

– phrases
play possum

• 1 feign unconsciousness or death (as an opossum does when threatened).

• 2 feign ignorance.

– origin C17: shortening of opossum.