when hell freezes over

常見例句

The only way to get rid of him short of a shotgun is to agree to meet up soon. Preferably, when hell freezes over.
擺脫他的最好辦法是說我先失陪過會(huì)再過來，當(dāng)然，等到地獄的冰化了再說吧。

And they say it will be when hell freezes over that they will accept anything remotely like a stimulus bill or any kind of a proposal you have out there to stimulate job growth through spending.
WHITEHOUSE: Presidential Press Conference
Besides, the state's would-be budget-balancers have tried almost everything else they can think of—short of imposing a personal income tax, which may come when hell, or at any rate Houston, freezes over.
ECONOMIST: Or, when is a new tax not a new tax?