preknock

例句：

1. 1.The bird preknocked at the window.
   鸟在窗户上啄了一下。
2. 2. She preknocked on the door to ask for help.
   她敲门求助。
3. 3. The tree was preknocked by a strong gust of wind.
   一阵强风把树给敲了。