pulsus undulosus

例句：

1. 1.The balloon was expanding in the wind.
   气球在风中膨胀。
2. 2. The ocean is experiencing an unusually large expansion.
   海洋正经历一次异常大的膨胀。
3. 3. The tree's roots were swelling with water.
   树的根因吸水而膨胀。