that cat won't jump

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.
See also: cat, jump, that
Farlex Dictionary of Idioms.

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.
See also: cat, jump, that
Farlex Partner Idioms Dictionary
See also:
  • at (one's) suggestion
  • at/on somebody's suggestion
  • on (one's) suggestion
  • suggestion
  • be in a dream world
  • flight of fancy
  • flight of fantasy
  • flight of imagination
  • a flight of fancy
  • perfection