[1] : The Collaborative International Dictionary of English v.0.48

cerulean \ceru"lean\, a. l. caeruleus.
   sky-colored; blue; azure. --cowper.
   1913 webster

         blue, blue, as if that sky let fall
   1913 webster

         a flower from its cerulean wall.         --bryant.
   1913 webster

[2] : WordNet (r) 2.0

cerulean
     adj : of a deep somewhat purplish blue color similar to that of a
           clear october sky; "october's bright blue weather"
           syn: azure, sky-blue, bright blue
     n : a light shade of blue syn: azure, sapphire, lazuline,
          sky-blue
see also:
azure sky-blue bright blue sapphire lazuline 

[3] : Moby Thesaurus II by Grady Ward, 1.0

49 moby thesaurus words for "cerulean":
   caelus, air, azure, azure-blue, azure-colored, azurean, azured,
   azureous, beryl-blue, berylline, blue, blue sky, bluish, caelum,
   canopy, canopy of heaven, ceruleous, cerulescent, cope, cyanean,
   dark-blue, deep-blue, empyrean, ether, firmament, heaven, heavens,
   hyaline, lift, lifts, light-blue, lightish-blue, livid, pavonian,
   pavonine, peacock-blue, sapphire, sapphirine, sky, sky-blue,
   sky-colored, sky-dyed, starry heaven, the blue, the blue serene,
   turquoise, vault, vault of heaven, welkin

[4] : U.S. Gazetteer (1990)

cerulean, ky
  zip codes: 42215

Cerulean >> C Words
Cerulean, definition of term: Cerulean
cerulean_pag1.html

Cerulean Blue >> C Words
Cerulean Blue, definition of term: Cerulean Blue
cerulean+blue_pag1.html