a pipe dream
pipe dream
A dream or idea that is impossible to accomplish. Many say that achieving world peace is a pipe dream because human beings are so flawed in their logic and emotions.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a pipe dream
If you describe something that someone wants to do or happen as a pipe dream, you mean that it is not realistic and will probably not happen. Oh, Toddy, it's a pipe dream. The banks won't lend you that sort of money. He said the figures showed that a third runway at the airport remained a pipe dream. Note: This expression refers to the sort of idea that someone is likely to have when they are smoking a drug in a pipe.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012
a ˈpipe dream
a hope, belief, plan, etc. that will probably never come true: She’s got this pipe dream about being a pop star.This expression refers to smoking the drug opium, which makes you sleep and gives you powerful dreams.Farlex Partner Idioms Dictionary © Farlex 2017