noun (n)

• a white crystalline oxide used in the production of calcium hydroxide(noun.substance)

  Synonym:
  burnt lime, calcined lime, calcium oxide, calx, fluxing lime, lime, unslaked lime
  

  source: wordnet30
• Calcium oxide; unslacked lime; -- so called because when wet it develops great heat. See 4th Lime, 2.(noun)

  source: webster1913