to plagiarize - "Take and use as one’s own (the thoughts, writings, inventions etc., of another person); copy (literary work, ideas etc.) improperly or without acknowledgement; pass off the thoughts, work, etc., of (another person) as one's own."
From: The New Shorter Oxford English Dictionary.
See the SFC Library Guide on how to avoid plagiarism.
View fact sheet on plagiarism from Elsevier.
There are 3 ways to incorporate other people's ideas and writing into your own work:
Quotations: Direct quote of the source material that is attributed to the original author.
Paraphrasing: Rewriting the original material in your own words (not just replacing individual words with synonyms). Must be attributed to original author.
Summarizing: A recap of the main point(s) of the original text in your own words. Attribute this to the original author as well.
For more information on how and when to use quotations, paraphrasing and summarizing visit the Online Writing Lab at Purdue University where they have a wealth of information on Research and Citation.