Plagiarism is one of the issues of academic integrity covered in the UNC Honor Code.
The UNC Instrument of Student Judicial Governance defines plagiarism as the:
Deliberate or reckless representation of another’s words, thoughts, or ideas as one’s own without attribution in connection with submission of academic work, whether graded or otherwise. (5)
In layman's terms, plagiarism is representing the work or words of another person as your own without appropriate attribution. This includes using your own previous work and not citing it appropriately, which is called self-plagiarism.
The Instrument defines self-plagiarism as:
Submitting an assignment that is the same as or substantially similar to one’s own previously submitted work(s) without explicit authorization of the instructor.
Implication: You cannot reuse assignments from one class in another without the prior approval of your instructor.