PHRASE
难以付诸实施的构想（或计划）；渺茫的希望；空口的许诺
If you describe an idea, plan, or promise of something good as pie in the sky, you mean that you think that it is very unlikely to happen.
例句
The true regeneration of devastated Docklands seemed like pie in the sky...
遭毁坏码头区的真正重建看起来希望渺茫。
He can't help thinking it's all just 'pie in the sky' talk.
他禁不住想所有这些不过是“画饼充饥”的空话而已。