Plagiarism is concerned with proper attribution—making it clear who the author or creator of a work or excerpt is. It is independent of copyright infringement, which has to do with whether and how one is allowed to reproduce the work. Properly attributing content does not release you from the responsibilities and limitations of copyright law. Similarly, the exceptions to copyright law do not cover you in terms of plagiarism.
UNC's Student Code of Conduct (BEAR Code) defines plagiarism as
"the use of another person’s work or reuse of your own work without giving proper credit to the original source."
Plagiarism can be:
UNC's Statements Regarding Plagiarism & Misconduct: