Relevant Search Plugin
Relevanssi can replace the default search option on your site where results are sorted in order of relevance, instead of by date. One of the most annoying problems with WordPress to date has been customizing the default search results… that is until now.
The plugin is customizable so that it can be setup to do fuzzy matching on partial words.
Content can be found by matching on just one search term or it can be required that all words be found.
There is a free version of Relevanssi that supports a single site, while the premium version offers multi-site support along with other features.