IPA: /ˈdʒʌstɪfaɪəbli/
KK: /dʒʌstɪfaɪəbli/
In a way that is reasonable or can be defended with good reasons.
She justifiably felt proud of her achievements after all the hard work she put in.
Justifiably → It is formed from "justus" (meaning just or right) and "-fy" (meaning to make) combined with the adverbial suffix "-ably" (meaning in a manner). The word "justifiably" means in a manner that is just or right, indicating that an action or decision is defensible or reasonable.
Think of 'just' meaning fair or right, and 'fy' meaning to make something. So, when something is done 'justifiably', it is made to be fair or reasonable.