According to the Oxford English Dictionary, plagiarism is:
"plagiarism, n.". OED Online. June 2011. Oxford University Press. 22 August 2011 <http://www.oed.com/view/Entry/144939>.
According to Merriam-Webster's Online Dictionary, plagiarize means:
"plagiarize, v." Merriam-Webster Online. 2011. Merriam-Webster, Inc. 22 August 2011 <http://www.merriam-webster.com/dictionary/plagiarize>.
Adapted from the L.V. Johnson Library, Plagiarism, Copyright & Fair Use