noun (n)

• a modifier that has little meaning except to intensify the meaning it modifies(noun.communication)

  Example:
  `up' in `finished up' is an intensifier.
  `honestly' in `I honestly don't know' is an intensifier.
  

  Synonym:
  intensive
  

  source: wordnet30
• One who or that which intensifies or strengthens; in photography, an agent used to intensify the lights or shadows of a picture.(noun)

  source: webster1913