(1):

(n.) The faculty or power of voluntarily producing light, as in the firefly and glowworm.

(2):

(n.) The light thus produced; luminosity; phosphorescence.

(3):

(n.) Any emission of light not ascribable directly to incandescence, and therefore occurring at low temperatures, as in phosphorescence and fluorescence or other luminous radiation resulting from vital processes, chemical action, friction, solution, or the influence of light or of ultraviolet or cathode rays, etc.