pipe dream (来源：www.EnglishCN.com)

【口】幻想;空想;白日梦

其中 pipe 有导管、烟斗等意思，在口语中pipe也指“容易干的事”

例句：

Father's plan to build a forest cabin by the lake was just a pipe dream.
父亲想在湖滨筑一林中小屋的计划不过是个美梦罢了。

“When I talk about gold medals, I’m not talking about a pipe dream, or thinking that they’re going to fall from the sky. These are athletes who have made the marks to achieve it,”
说到金牌，我可不是在做白日梦或者认为它们是从天而降的。我们那些已经取得佳绩的运动员会把它变成现实。