an act or instance of using or closely imitating the language and thoughts of another author without authorization and the representation of that author's work as one's own, as by not crediting the original author: It is said that he plagiarized Thoreau's plagiarism of a line written by Montaigne.
a piece of writing or other work reflecting such unauthorized use or imitation: “These two manuscripts are clearly plagiarisms,” the editor said, tossing them angrily on the floor.
1620s, from -ism + plagiary (n.) "plagiarist, literary thief" (1590s), from Latin plagiarius "kidnapper, seducer, plunderer, one who kidnaps the child or slave of another," used by Martial in the sense of "literary thief," from plagiare "to kidnap," plagium "kidnapping," from plaga "snare, hunting net," perhaps from PIE *plag- (on notion of "something extended"), from root *plak- (1) "to be flat" (see placenta).
Literary theft. Plagiarism occurs when a writer duplicates another writer's language or ideas and then calls the work his or her own. Copyright laws protect writers' words as their legal property. To avoid the charge of plagiarism, writers take care to credit those from whom they borrow and quote.
Similar theft in music or other arts is also called plagiarism.