adventive /ədˈvɛntɪv/adjective 3noun 1forms 3 adjective3 •Accidental. •Of a plant: not native, but introduced by humans to a place and since naturalized. •(no longer used) Adventitious. noun1 •A non-native plant that has become naturalized.Such interlopers are known as exotics, adventives, or aliens, all terms that may be considered synonymous with "nasty. — 1988 formsadventives · more adventive · most adventive