illumination UK /ɪˌl(j)umɪˈneɪʃən/US /ɪˌlumɪˈneɪʃən/ noun5 •The act of illuminating, or supplying with light; the state of being illuminated.The room was filled with soft illumination from the candles. •Festive decoration of houses or buildings with lights. •(figurative) Enlightening influence; inspiration.The philosopher’s work gave intellectual illumination to many. •Adornment of books and manuscripts with colored illustrations. See illuminate (transitive verb). •(figurative) Splendour; brightness. formsilluminations