The process by which, in a few hours, a weak page can be turned into a valid entry with enough examples to satisfy those who petitioned for its deletion.
Sometimes, someone creates an entry with a funny lead-in but no examples, or a duplicate of an existing entry. After someone complains about it, one of two things happen. The entry is deleted, or a group of editors work the Wiki Magic, reformatting the entry and creating examples so that it stands on its own or is different from the other trope. Occasionally, a trope is so sparse that the entry becomes built up on different assumptions than the intended one, but is left alone because it's just that good.
The majority of articles come out stronger for this process, as it forces people to write for the readers (and a highly critical set of readers at that), rather than themselves.
Please note that going through the proper procedure to introduce a trope will help ensure your page is strong to begin with — nowadays a weak page with no TLP is more likely to be deleted with a request to submit it to the scrutiny of the Hive Mind first.
If you're a kind soul who's looking to give out a little Wiki Magic, go over to Needs Wiki Magic Love for a list of pages currently in need of Magic.