in ‧ ex ‧ cu ‧ sa ‧ ble /ˌɪnɪkˈskjuːzəb ə l◂/ BrE AmE adjective
[ Word Family: verb : ↑ excuse ; noun : ↑ excuse ; adverb : ↑ inexcusably ; adjective : ↑ excusable ≠ ↑ inexcusable ]
inexcusable behaviour is too bad to be excused:
an inexcusable act of aggression
—inexcusably adverb