In layman's terms photographic plagiarism occurs when one photographer copies the work of another photographer, by making a new image that is so similar to the image being copied that any viewer looking at the two images is struck by their overwhelming correlation.
You'll soon see what I mean when you look through the examples in the articles below. Having seen blatant plagiarism of my wife Magda Indigo's work on Flickr I decided to write a blog on the topic. However I soon discovered that the subject of photographic plagiarism has been covered extensively, so I refer you to a selection of articles which I found interesting...
There is nothing better than coming up with something new. To stand out from the crowd you need to do something different, carve a new path. Be a leader, not a follower. As the old saying goes, we stand on the shoulders of giants who have come before us, so by all means my advice is to look and learn from the masters, but then do some original with that knowledge. To slavishly copy and then pass other people's creative ideas off as your own work is not flattery, its the last resort of the creatively bankrupt.