用頭撞牆;徒勞無益;枉費心機
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.試圖和他們講道理只是白費口舌。
釋義來自《牛津高階英漢雙解詞典》第 9 版