important UK /ɪmˈpɔː.tənt/US /ɪmˈpɔɹ.tənt/ adjective2 •mattering a lot, because it has a big effect or great valueWe thought it important for there to be a fire escape at the back of every building. •(no longer used) Pompous; self-important. formsimportanter · more important · importantest · most important