beat one's brain(s) out 絞盡腦汁，但常無法成功

說明：

這句和 rack one's brain 的意義十分相似，但常隱含失敗的意思。如果主詞是複數，則 brain 要加 s。

例子：

Mr Wong is beating his brain out. He has been trying to get a loan from a bank. But it seems to be totally hopeless.

by Thomas Shum