1. A material that sends out light by absorbing and then converting a portion of incident energy: The students observed that the ocean was glowing and concluded that there was a lot of luminophore in the water which absorbed radiation and produced a glowing effect.
2. An atom or atomic grouping in an organic compound that increases its ability to produce light: The marine biologists were studying how to increase the luminophore in certain oceanic organisms and thereby increase the ability of such organisms to phosphoresce.