A more like this query is a passage of natural language text that has more than a threshold number of terms (the default is 12, but can be configured by the administrator with the likeMin configuration setting in solrconfig.xml). All terms will be implicitly ORed. This may result in a large number of results, but automatic bigram and trigram relevancy boosting will tend to rank results that more closely match the query text. Two applications of this feature are to detect plagiarism and derivative works or subtle variations. Exact matches will rank highest, but close matches will also rank high. For example:
When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.
All of that text would typically be pasted into the query box as one line of text.
Be sure not to enclose the passage in double quotation marks, otherwise the query will be treated as a precise phrase query. There is no harm in using the quoted phrase, other than that an exact match must be made in that case.
This feature may be suppressed by simply enclosing the entire query within parentheses:
(When in the Course of human events, it becomes necessary for one people to dissolve ... )