This is the adverb of unarguable: it drops into a sentence to say "and nobody can dispute this part". Usually it sits right in front of the thing being claimed — "unarguably the finest hotel in the city", "the plan was unarguably a success" — or it opens a sentence to stamp the whole statement as settled. It is a writer's word: reviews, editorials, business reports, formal speeches. In conversation people just say "definitely", "no question", or "you can't argue with that". Be aware of what a native reader hears when you use it. Because the speaker is announcing that no argument is possible, it can sound confident and generous when the fact really is plain, and a little pushy when it is not. Reviewers reach for it when praising: it makes the praise sound like a measurement rather than an opinion. Its close cousins undeniably and indisputably do the same job; unarguably is the least common of the three, so it stands out slightly on the page.

無可爭辯地、毫無疑問地（放在名詞或形容詞前面加強語氣）。