IPA: /bɪˈliːvəblɪ/
KK: /bɪˈlivəbli/
In a way that is easy to believe or accept as true.
She explained the situation so believably that everyone trusted her.
Believably → It is formed from "believe" (from Old English "beliefe", meaning to accept as true) and the suffix "-ably" (meaning in a manner that can be). The word "believably" means in a manner that can be accepted as true or credible.
Think of 'believe' as accepting something as true, and '-ably' means in a way that can be. So, believably means something can be accepted as true.