implausibly

This adverb carries a strong connotation of skepticism. It is typically used to describe a claim, excuse, or narrative that fails the test of common sense or logic, suggesting that the speaker finds the situation far-fetched or deceptive.

In professional or legal contexts, it is often used to highlight a lack of credibility in testimony. It differs from "unbelievably" in that "unbelievably" can be used for positive emphasis (e.g., unbelievably talented), whereas "implausibly" is almost exclusively used to denote a failure of logic or truthfulness.