mottling

例句：

1. 1.The boat was moulting over the waves.
   船在波浪中颠簸。
2. 2.The river is undulating through the valley.
   河流在山谷中蜿蜒流淌。
3. 3. The train was moulting through the tunnel.
   火车在隧道中颠簸行驶。