IPA: /dɪˈbeɪtəblɪ/
KK: /dɪˈbeɪtəbli/
In a manner that can be argued or questioned; open to discussion.
The proposal is debatably the best option for the project.
Debatably → It is formed from "debate" (from Old French *debattre*, meaning to fight or contend) and the suffix "-ably" (meaning in a manner that can be). The word "debatably" means in a manner that can be debated or argued.
Think of the word 'debate' as a discussion where people argue different sides, and '-ably' means it can be done in that way. So, debatable means something that can be argued about.