pie in the sky
pie是“馅饼、派”的意思。pie in the sky 天上的馅饼，就是指：不切实际的想法，不能兑现的诺言，相当于中文里我们常说的“空中楼阁、空头支票”。
It's crunch time. Your idea is just pie in the sky.
现在是紧要关头，你的想法是不切实际的。
In my book, his promises are often pie in the sky. It's out of the question for him to get the work done during such a short time.
据我所知，他的承诺常常是空头支票。他不可能在这么短的时间内把工作做完。
下面我们再来看几个和这个口语表达有关的例句：
Don't hold out for pie in the sky. Get real!
别总想着天上掉馅饼，现实点吧!
When something is just pie in the sky, it looks good but it's unlikely to happen.
当我们说空中楼阁，就是说看起来很美好，却不大可能实现。
Their plans to set up their own business are just pie in the sky.
他们要创办公司的种种计划都是空的。
另外，pie in the sky 中间加上连字符，还可以作形容词使用。
Get rid of your pie-in-the-sky ideas!
不要有那些异想天开的想法。
It's all just pie-in-the-sky talk!
这只不过是天方夜谭。
Do you believe all of their pie-in-the-sky promises?
你会相信他们所有的空头承诺吗？
