The phrase denotes an ambitious, seemingly impossible endeavor. It characterizes actions that are audacious, bordering on the fantastical, and often exceeding conventional limitations. As an idiom, it paints a picture of someone attempting to achieve something perceived as utterly unattainable.
The implied significance of undertaking such an ambitious task resides in the potential for transformative impact, even if the literal goal remains out of reach. The effort and innovation required to even attempt the impossible can lead to unexpected breakthroughs and advancements. Historically, many scientific and technological leaps started as concepts deemed unrealistic, highlighting the value of pursuing bold visions.