General:
* Implausible: This word indicates that the story is unlikely or unbelievable, based on logic or common sense.
* Unbelievable: This is a direct statement that the story is not believable.
* Outlandish: This word suggests that the story is excessively strange or improbable.
* Incredible: This word implies that the story is so extraordinary that it's hard to believe.
* Fantastic: This word suggests that the story is imaginative or unreal.
More specific:
* Far-fetched: This word suggests that the story is highly improbable or unrealistic.
* Preposterous: This word emphasizes the absurdity or ridiculousness of the story.
* Ridiculous: This word suggests that the story is so foolish or nonsensical that it's laughable.
* Bogus: This word implies that the story is false or fabricated.
* Unrealistic: This word indicates that the story doesn't reflect reality.
More subtle:
* Questionable: This word suggests that the story is suspect or doubtful.
* Dubious: This word implies that the story is uncertain or unreliable.
* Suspect: This word indicates that the story is likely false or misleading.
* Implausible: This word implies that the story is not credible or believable.
The best word to use will depend on the specific context and the type of disbelief you want to convey.