inexcusable
adjective
ˌɪnɪkˈskjuːzəbl 
ˌɪnɪkˈskjuːzəbl too bad to accept or forgive
Synonym
unjustifiableinexcusable rudenessOpposite
excusableinexcusably ˌɪnɪkˈskjuːzəbli ˌɪnɪkˈskjuːzəbli 
Definition of inexcusable adjective from the Oxford Advanced Learner's Dictionary
ˌɪnɪkˈskjuːzəbl ˌɪnɪkˈskjuːzəbl ˌɪnɪkˈskjuːzəbli ˌɪnɪkˈskjuːzəbli 