IPA: /ʌnˈdʒʌstɪfaɪəbli/
KK: /ʌnˈdʒʌstəˌfaɪəbli/
In a way that cannot be justified or explained as reasonable or fair.
The decision was made unjustifiably, leaving many people confused and upset.
Unjustifiably → It is formed from "un-" (meaning not), "just" (from Latin "justus", meaning lawful or right), and "-ifi" (from Latin "facere", meaning to make) combined with "-able" (meaning capable of). The word means not capable of being made lawful or right, hence lacking justification.
Think of 'not' ('un-') making something 'lawful' or 'right' ('just') and 'capable of being made' ('-able'). This helps you remember that 'unjustifiably' means something that cannot be justified.