You can extend default WordPress search feature to show relevant results even if the query you entered matches a single word in any blog post, this way your WordPress search box will find those posts that contain any of the words entered instead of only posts that contain all of the words searched. It makes WordPress search use OR operator instead of default AND operator
To start up using this feature in you WordPress site all you need to do is install and activate Any Word Search plugin and you are done. There are no options and configuration settings page to work on. After activation its functionality gets added to default WordPress search.