You think something is impossible (or very unlikely). "There's no way we're going to finish before five." "There's no way that the prime minister will agree to sign this bill." You won't or can't do something. "There's no way I'm going out in this rain." "There's no way I'm going to agree to this." "There's no way I can run that fast."

It is not impossible or someone will not do it.

It means "It is not possible." Plain and simple explanation. :-)

you can say that when you won't do sth, or you can't because it's almost impossible