noun (n)

• a secondary and sometimes unexpected consequence(noun.phenomenon)

  Synonym:
  by-product
  

  source: wordnet30
• a product made during the manufacture of something else(noun.artifact)

  Synonym:
  by-product, spin-off
  

  source: wordnet30
• A secondary or additional product; something produced, as in the course of a manufacture, in addition to the principal product.(noun)

  source: webster1913