inveterate
definition
having a particular habit, activity, or interest that is long established and unlikely to change
example
Despite his many attempts to quit, he remained an inveterate smoker, lighting up a cigarette the moment he stepped outside.
synonyms
incorrigiblehabitualchronic
word origin — From Latin 'inveteratus', past participle of 'inveterare', meaning 'to make old' or 'to grow old in'.