noun (n)

• a sizeable hole (usually in the ground)(noun.object)

  Synonym:
  pit
  

  source: wordnet30
• space that is surrounded by something(noun.shape)

  Synonym:
  enclosed space
  

  source: wordnet30
• soft decayed area in a tooth; progressive decay can lead to the death of a tooth(noun.process)

  Synonym:
  caries, dental caries, tooth decay
  

  source: wordnet30
• (anatomy) a natural hollow or sinus within the body(noun.body)

  Synonym:
  bodily cavity, cavum
  

  source: wordnet30
• Hollowness.(noun)

  source: webster1913