According the Cornell's College of Arts and Sciences "Recognizing and Avoiding Plagiarism" tutorial, "Plagiarism is the unacknowledged use of the words or ideas of others." Often plagiarism is not recognized as such, but that doesn't help if you run of the Code of Academic Integrity!
"All of the following are considered plagiarism:
- turning in someone else’s work as your own
- copying words or ideas from someone else without giving credit
- failing to put a quotation in quotation marks
- giving incorrect information about the source of a quotation
- changing words but copying the sentence structure of a source without giving credit
- copying so many words or ideas from a source that it makes up the majority of your work, whether you give credit or not (see our section on “fair use” rules"
-from the "Handout on Plagiarism and Citation", originally created by Turnitin.com and modified by Medha Devare for educational use