1. Full of effulgence; describing the emission of visible radiation: The night sky was the most luminous Jeff had seen during his vacation, simply glittering with starlight.

Max has a watch with a luminous face which can be seen when it is dark.

2. Emitting or reflecting lucency, with or without accompanying heat: The most luminous life in the sea tends to dazzle an eerie green under the night sky.
3. Immensely bright or brightly colored: The luminous illustration in the hand-printed text drew the reader's attention to the fine designs and complimentary colors.
4. Evaluated on the basis of the visual sensation produced in an observer rather than energy measurements: Sarah gave a luminous performance of the role as Marie in the first play of the summer season.