In a way that does not make people believe you. It is the adverb of 'unconvincing', so it describes HOW someone speaks, acts or performs — and it very often adds a small, dry comment from the writer. Look at 'He smiled unconvincingly': the writer is telling you the smile was fake and that everyone could see it. That is the flavour of this word — it lets a narrator raise an eyebrow. You will meet it most in storytelling and in reviews, glued to verbs of speaking and pretending: say, argue, claim, protest, deny, smile, laugh, pretend, act. 'Not very convincingly' means the same thing and sounds more natural in conversation; the single word is tidier on the page. In sports writing it has its own life: to 'win unconvincingly' means to get the victory while looking weak, which pleases nobody.

沒有說服力地、（說得）讓人不太相信地