noun (n)

• someone who uses another person's words or ideas as if they were his own(noun.person)

  Synonym:
  literary pirate, pirate, plagiariser, plagiarizer
  

  source: wordnet30
• One who plagiarizes; or purloins the words, writings, or ideas of another, and passes them off as his own; a literary thief; a plagiary.(noun)

  source: webster1913