that cat won't jump
There's no way that idea will work; that suggestion is unrealistic or completely unfeasible. I hear many saying that we ought to do away with taxes altogether, but I'm afraid that cat won't jump.
that cat won't jump
that suggestion is implausible or impracticable. informal 1965 Simon Troy No More a-Roving If you're telling me she fell in, just like that—oh no! That cat won't jump.