facedown

例句：

1. 1.The baby was sleeping on his back, face down.
   宝宝正脸朝下躺着睡觉。
2. 2.He turned the page of the book face down.
   他翻到书的背面。
3. 3.She faced the wall and turned her back to him.
   她面对墙，背对着他。