bioluminescence
    n 1: luminescence produced by physiological processes (as in the
         firefly)

Luminescence \Lu`mi*nes"cence\, n. [See Luminescent.]
   1. (Physics) 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.
      [Webster 1913 Suppl.]

   2. (Zool.)
      (a) The faculty or power of producing light by biological
          processes, as in the firefly and glowworm. Also called
          bioluminescence.
      (b) The light produced by biological or biochemical
          processes. Also called bioluminescence.
          [Webster 1913 Suppl. +PJC]

Bioluminescence \Bi"o*lu`mi*nes"cence\
   (b[imac]"[-o]*l[=oo]`m[i^]*n[e^]s"ens), n. [Gr. bi`os life +
   luminescence.]
   a type of luminescence produced by biological or
   biochemical processes, such as a glowworm glow or the action
   of luciferase on luciferin. A well-known example is that of
   firefly luminescence. See also luciferin.
   [PJC]