用头撞墙;徒劳无益;枉费心机
be banging, etc. your head against a brick wall
to keep trying to do sth that will never be successful
Trying to reason with them was like banging my head against a brick wall.试图和他们讲道理只是白费口舌。
释义来自《牛津高阶英汉双解词典》第 9 版