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.
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.