IPA: /ɪnˈɛk.skjʊ.zə.bəl/
KK: /ɪnˈɛk.skjʊ.zə.bəl/
Something that cannot be justified or excused; it is considered unacceptable or wrong.
His inexcusable actions led to serious consequences.
Inexcusable → It is formed from "in-" (meaning not) and "excusare" (meaning to free from blame or to excuse) and the suffix "-able" (meaning capable of). The word "inexcusable" means not capable of being excused or justified.
Think of 'not' ('in-') being able to 'free from blame' ('excusare') — that's why inexcusable means something that cannot be justified.