Luminous, a.
Etymology: [L. luminosus, fr. lumen light: cf. F. lumineux. See Luminary, Illuminate.]
1. Shining; emitting or reflecting light; brilliant; bright; as, the is a luminous body; a luminous color. Fire burneth wood, making it . . . luminous. Bacon. The mountains lift . . . their lofty and luminous heads. Longfellow.
2. Illuminated; full of light; bright; as, many candles made the room luminous. Up the staircase moved a luminous space in the darkness. Longfellow.
3. Enlightened; intelligent; also, clear; intelligible; as, a luminous mind. " Luminous eloquence." Macaulay. " A luminous statement." Brougham. Luminous paint, a paint made up with some phosphorescent substance, as sulphide of calcium, which after exposure to a strong light is luminous in the dark for a time.
Syn. -- Lucid; clear; shining; perspicuous. -- Lu"mi*nous*ly, adv. -- Lu"mi*nous*ness, n.
Shades of meaning
Fernald lists luminous only as an antonym, under dark.
He lists it without comment; the entries above explain its neighbors.