noun (n)

• an extended communication (often interactive) dealing with some particular topic(noun.communication)

  Example:
  The book contains an excellent discussion of modal logic.
  

  Synonym:
  discourse, treatment
  

  source: wordnet30
• an exchange of views on some topic(noun.communication)

  Example:
  We had a good discussion.
  

  Synonym:
  give-and-take, word
  

  source: wordnet30
• The act or process of discussing by breaking up, or dispersing, as a tumor, or the like.(noun)

  source: webster1913