We are now operating at a loss.

我们现在是亏本经营。

I'm at a loss what to do next.

我对下一步做什么心里没谱。

I was at a loss for what to do next.

我不知道下一步该怎么办。

His comments left me at a loss for words.

他的评论让我不知说什么才好。

Detectives are so far at a loss to explain the reason for his death.

至今侦探仍茫然无法解释他的死因。