scour something out
phrasal verb with scour verb uk/skaʊər/ us/ˈskaʊ.ɚ/
冲刷出；磨出
to make a hole by a movement that is repeated continuously over a long period of time
The fast-moving water had scoured out a channel in the rock. 急流在岩石上冲刷出一道凹槽。