From Longman Dictionary of Contemporary Englisharguablyar‧gu‧a‧bly /ˈɑːɡjuəbli $ ˈɑːr-/ ●○○ adverb [sentence adverb] used when giving your opinion to say that there are good reasons why something might be true Senna was arguably the greatest racing driver of all time.
Examples from the Corpus
arguably• If Glenn McGrath, arguably currently the world's finest fast bowler, drops a short one, cut or hook him.• Although first written in 1951, this description of the content and impacts of constitutions is arguably still the best.• Sketchpad was not only the first drawing program, but was arguably the best, absurdly ahead of its time.• Contact between school and business leads naturally to, arguably, the most fruitful area for partnership - curriculum enhancement. 