It's a one-word way to say "there might be something wrong with this idea." It might be clear from the context what the wrongness might be, or it might be a ga

It's a one-word way to say "there might be something wrong with this idea." It might be clear from the context what the wrongness might be, or it might be a gateway for more elaboration/discussion. It seems like a perfectly fine construction to me, and a good example of the efficiency mentioned in the grandparent comment.