n. Supply of light; emanation of luminous rays; light afforded by a luminous body or substance.n. The act of illuminating, or the state of being illuminated; a lighting up; specifically, an unusual or profuse display of light; decoration by means of many lights, as in festivity or rejoicing: as, the illumination of a city.n. Mental enlightenment; knowledge or insight imparted.n. In a special use, the doctrine of the Illuminati; worship of enlightenment or knowledge.n. Pictorial ornamentation of books and manuscripts by hand, as practised in the middle ages; adornment by means of pictures, designs, and letters in flat colors, gilt, etc., practised especially in devotional works: as, the art of illumination.n. A representation or design in an illuminated work: as, the illuminations of a psalter.n. Specifically, the measure of the amount of light falling on a surface.n. In the pictorial arts, the quality and quantity of light expressed.