the point at which it is no longer possible to continue with a process or activity

We've struggled on for as long as we could, but now we're at the end of the line. 我们一直在尽己所能勉力维持，但是现在我们是山穷水尽了。

When the bank refused to lend us any more money we realized we'd reached the end of the road. 当银行拒绝再给我们贷款的时候，我们意识到已经走投无路了。