The Collaborative International Dictionary of English v.0.48:

Phosphor \Phos"phor\ (f[o^]s"f[^o]r or f[o^]s"f[o^]r), n. [Cf.
   G. phosphor. See Phosphorus.]
   1. Phosphorus. [Obs.] --Addison.
      [1913 Webster]

   2. The planet Venus, when appearing as the morning star;
      Lucifer. [Poetic and Rare] --Pope. --Tennyson.
      [1913 Webster]

   3. A phosphorescent substance. [archaic]
      [PJC]

   4. A substance capable of exhibiting luminescence. This term
      is now most commonly used to refer to substances used in
      fluorescent lights, image intensifiers, or cathode-ray
      tubes (CRT's), which luminesce when excited by ultraviolet
      radiation or an electron beam. In color CRT's, three
      different phosphors, each giving different colors when
      excited, are used.
      [PJC]

WordNet (r) 3.0 (2006):

phosphor
    n 1: a synthetic substance that is fluorescent or
         phosphorescent; used to coat the screens of cathode ray
         tubes

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "phosphor":
   autoluminescence, bioluminescence, candle fly,
   cathode luminescence, chemicoluminescence, chemiluminescence,
   corposant, crystalloluminescence, double corposant,
   electroluminescence, fata morgana, fire beetle, firefly, fireworm,
   fluorescence, fox fire, glowworm, ignis fatuus, lampyrid,
   lantern fly, lightning bug, luciferase, luciferin, luminescence,
   luminophor, marshfire, noctiluscence, phosphorescence,
   photoluminescence, radioluminescence, thermoluminescence,
   tribofluorescence, triboluminescence, tribophosphorescence, wisp,
   witch fire



Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "Phosphor":
   Aldebaran, Canicula, Dog Star, Hesper, Hesperus, Lucifer,
   North Star, Phosphorus, Polaris, Sirius, Venus, Vesper,
   celestial body, comet, daystar, evening star, fixed stars,
   heavenly body, living sapphires, lodestar, morning star, orb,
   polar star, polestar, sphere, starry host, stars