From Merriam-Webster's online dictionary, a definition:
This excerpt below is from Cañada College's Academic Integrity Policy and the Student Conduct Code.
Academic Integrity (Cheating and Plagiarism)
As members of the college community, students at Cañada are expected to demonstrate integrity in all academic endeavors. Students are evaluated on their own merits, so they should protect academic integrity at Cañada College and be proud of their achievements.
General principles of academic integrity include the concept of respect for the intellectual property of others, the expectation that individual work will be submitted unless otherwise allowed by an instructor, and the obligations both to protect one’s own academic work from misuse by others and to avoid using another’s work as one’s own. Faculty, with the full support of the college, have the right to take standards of academic integrity into account when assigning grades. All students are expected to understand and abide by these principles.
Any act which gains or is intended to gain an unfair academic advantage or which compromises the integrity of the academic standards of the college may be considered an act of academic dishonesty.
Cheating and Plagiarism are violations of the Academic Integrity Policy and the Student Conduct Code and will result in appropriate disciplinary action.
Cañada College students, like many and community college students, are extremely busy, often with jobs, families and outside responsibilities that leave them pushed for time when it comes to writing papers.
Whether students mean to plagiarize or not, the consequences of an author's words or phrasing appearing in your work can mean a failing grade on your paper, a failing grade in a class or expulsion from college. To avoid any of these, keep careful track of where you find your sources and quotes. Index cards, careful notes that include citation information, a Google doc - it doesn't matter how you keep words and ideas next to the author's name, the title of the work and page numbers.
Many students "patch together" thoughts in a recognizable form of writing known as "patchwriting." Read more here.
Purdue University's Online Writing Lab, the famous OWL, offers an exhaustive plagiarism guide that is worth consulting.
From Harvard to high school, students caught cheating:
"Administrators said that on final-exam questions, some students supplied identical answers, down to, in some cases, typographical errors, indicating that they had written them together or plagiarized them."