A confused fantastic ‘dream’ or mental illusion produced by smoking opium; hence, figuratively, any fantastic or illusory notion.(noun)
The Century Dictionary (Public Domain)
Use "pipe-dream" in a sentence
"Even more tragic is that The Call, a wing of the New Apostolic Reformation aka Seven Mountains Movement has tremendous ambition but will always be numerically too small to fulfill its pipe-dream of earthly dominion."
"It might be a pipe-dream but I don't think it's unreasonable so I ain't giving up hope yet. posted by Hal Duncan | 8: 32 PM"
"Maybe I would have adopted some other pipe-dream — I hear there's money in acting."