il·lu·mi·nate / iˈloōməˌnāt/ • v. [tr.] light up: a flash of lightning illuminated the house | fig. his face was illuminated by a smile. ∎  decorate (a building or structure) with lights for a special occasion. ∎  [often as adj.] (illuminated) decorate (a page or initial letter in a manuscript) with gold, silver, or colored designs. ∎  [usu. as adj.] (illuminating) fig. help to clarify or explain (a subject or matter): a most illuminating discussion. ∎  enlighten (someone) spiritually or intellectually.DERIVATIVES: il·lu·mi·nat·ing·ly adv.il·lu·mi·na·tive / -ˌnātiv; -nətiv/ adj.il·lu·mi·na·tor / -ˌnātər/ n.

illuminate light up, give light to XVI; decorate with colour XVIII. f. pp. stem of late L. illumināre, f. IL-1 + lūmen, lūmin- LIGHT1; see -ATE2.
So illumination spiritual enlightenment XIV; lighting up XVI; embellishment with colour XVII. — (O)F. — late L. illumine enlighten (first in spiritual sense). XIV. — (O)F. — L.