A pipe dream noun phrase
Used to refer to an impossible plan or idea
We will not be able to complete this project in one month. It is a pipe dream.
Their plan is impractical. It's nothing more than a pipe dream.
In the past, traveling to Mars was believed to be a pipe dream.
To deal with something when it happens without planning for it beforehand
Said when you believe something will never hapen
Impossible or unrealistic dreams, hopes, or plans
Something that is impossible to happen, to achieve, or to be done.
To consider or think about what will happen in the future