noun (n)

• the intellectual ability to penetrate deeply into ideas(noun.cognition)

  Synonym:
  astuteness, depth, profoundness, profundity
  

  source: wordnet30
• the quality of being physically deep(noun.attribute)

  Synonym:
  profoundness, profundity
  Antonym:
  shallowness
  

  source: wordnet30
• the extent downward or backward or inward(noun.attribute)

  Synonym:
  depth
  

  source: wordnet30
• a low pitch that is loud and voluminous(noun.attribute)

  source: wordnet30
• The state or quality of being deep, profound, mysterious, secretive, etc.; depth; profundity; -- opposed to shallowness.(noun)

  source: webster1913