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.
See also: dream, pipe
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.
See also: dream, 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.
See also: dream, pipe
Farlex Partner Idioms Dictionary © Farlex 2017
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References in periodicals archive ?
A pipe dream of size n is a filling of the staircase shape (n - 1, ..., 2, 1) where each box contains two crossing pipes + or two turning pipes [??].
Generalized triangulations, pipe dreams, and simplicial spheres
FOR ALL WE HEAR of the rapid pace of technological development, many users in the real world consider the following truths to be self-evident: Your notebook computer never has enough juice to finish a job on the go, and commercial fuel cells are a pipe dream decades away from realization.
One for the road: diminution and durability are the keys to a fuel cell future
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