It's quite difficult to provide the exact data as Google algorithm is Google's hidden treasure. Better to keep yourself safe by creating completely unique content, Referring to your example of Wikipedia definition, you can add something like " ACCORDING TO WIKIPEDIA ..... " while copying definition or adding reference links while copying any content from other sources.

Remember that Google is  not only giving importance to unique content but it should be of high quality. That means the article should be innovative like a complete new thing & well researched, so it mustn't be of 200 or less words. So Google will compare the quality of the whole article with the copied content & then it'll decide whether it's a duplicate content article or not.