adversarious UK /ˌæd.vəˈsɛəɹi.əs/US /ˌæd.vɚˈsɛɹi.əs/ adjective1 •(no longer used) hostile; adversarialIt is only when actually engaged in this vindication that I can regard you as an adversary: in the intervals, when that occupation is suspended, I am not sensible of any adversarious feeling — 1826 formsmore adversarious · most adversarious