You do or say something implausibly when the way it happens, or the claim itself, is hard to believe. “He implausibly claimed he had never seen the email.” Writers also put it before an adjective: implausibly young, implausibly lucky — meaning it surprises you because it does not seem likely. It is the adverb of implausible, with the same softer-than-impossible feel. Formal to neutral. Though actually, in speech people more often say unbelievably, which can also mean “very”; implausibly stays closer to “this does not sound true.”

難以置信地；不太可能地