When someone defines something on a sight such as Urban Dictionary, or answers a question on Yahoo! Answers that is exactly the same as the previous persons answer. To hide the fact that they did this, they usually add one or two extra words, or paraphrase part of the Definition.
EXAMPLE ONLY, not real UD definition
1st definition: Asian People
2nd definition: People who are Asian
Question: What are some good 360 games?
1st Response: Halo 3, Modern Warfare 2, Mass Effect 2, Fallout 3, Left 4 Dead 2
2nd Response: MW2, ME2, Halo 3, L4D2 and Assasins Creed 2
Both responses, the second person was Wikiplagiarising(plural for Wikiplagiarism)
For work in a paper or publication, using Wikipedia as the source of information that you don't give credit to; AND the information happens to be incorrect, adding insult to injury.
Bob's paper got an 'F' for blatant plagiarism. He lifted most of it from Wikipedia and assumed it was correct. The professor said it was the worst wikiplagiarism she'd seen in a long time.