play possum

play possum  {v. phr.},  {informal}

1. Претворяться спящим.

Johnny seemed to be fully asleep, but his mother knew that he was playing possum.

2. Быть тихим, неподвижным в целях самозащиты; пытаться избежать внимания при помощи пассивности.

The rabbit played possum under the bushes, hoping the hunter would not see him.