IPA: /ˈɑːɡjʊəbli/
KK: /ˈɑrɡjʊəbli/
In a way that can be supported by evidence or reasoning; it suggests that something is open to argument or debate.
Arguably, this is the best movie of the year.
Arguably is formed from "argue" (from Latin "arguere", meaning to make clear or to assert) and the suffix "-ably" (meaning in a manner that can be). The word "arguably" means in a manner that can be asserted or stated as a point of view.
Think of making a point clear ('argue') in a way that can be accepted ('-ably'). This helps you remember that 'arguably' means something can be stated as a valid opinion.