Source : Webster's Revised Unabridged Dictionary (1913)

Intensifier \In*ten"si*fi`er\, n.
   One who or that which intensifies or strengthens; in
   photography, an agent used to intensify the lights or shadows
   of a picture.

Source : WordNet®

intensifier
     n : a modifier that has little meaning except to intensify the
         meaning it modifies; "`up' in `finished up' is an
         intensifier"; "`honestly' in `I honestly don't know' is
         an intensifier" [syn: {intensive}]