According to the Oxford English Dictionary plagiarism is “The action or practice of taking someone else's work, idea, etc., and passing it off as one's own.” 1
In the American University system, plagiarism is a type of academic cheating and it is a violation of University of Massachusetts Boston Code of Student Conduct.
1. OED Online, s.v. "plagiarism,". accessed February 28, 2017 http://www.oed.com/view/Entry/144939?redirectedFrom=plagiarism.