From Longman Dictionary of Contemporary Englishinexcusablein‧ex‧cu‧sa‧ble /ˌɪnɪkˈskjuːzəbəl◂/ adjective BAD BEHAVIOUR OR ACTIONSFORGIVEinexcusable behaviour is too bad to be excused an inexcusable act of aggression —inexcusably adverb
Examples from the Corpus
inexcusable• Anyone can make a mistake, but to ignore basic safety regulations is quite inexcusable.• Being late for your own wedding is inexcusable.• It is inexcusable that the government has never paid a cent to the widows of these brave men. 