1. A computer-implemented method comprising: determining, using data associated with search queries submitted by past users of a search engine, that a particular search result selected by a particular, past user of the search engine includes a query term included in an initial search query, and a particular synonym that was generated for the query term included in the initial search query using a particular synonym rule, wherein the data associated with the search queries indicates that the particular search result was selected by the particular, past user of the search engine from among multiple search results that were generated by the search engine using the initial search query and one or more revised search queries that include the particular synonym for the query term; determining, using the data associated with the search queries, that a different search result that also includes the particular synonym for the query term was ranked above the particular search result and was not selected by the particular, past user of the search engine; in response to determining that (i) the particular search result selected by the particular, past user of the search engine includes the query term included in the initial search query, and the particular synonym for the query term, and (ii) the different search result that also includes the particular synonym for the query term was ranked above the particular search result and was not selected by the particular, past user of the search engine, incrementing a particular type of skip count for the particular synonym rule; and determining whether to revise a subsequently received search query that includes the query term included in the initial search query, to include the particular synonym for the query term, based at least on the particular type of skip count for the particular synonym rule.