as dead as a doornail字面意思“像门钉那样死了”，引申为死绝了；死透了；完全没希望了；确信无疑地死了；失效的。

【例句】
That idea from last week's meeting is as dead as a doornail, because the boss has vetoed it.
上星期开会提出来的那个点子，既然已经被大老板否决了，那就绝对没戏了。

The treaty may be considered to be as dead as a doornail.
这项条约可以认为是完全作废了。