Synonym dictionary is another powerful tool in searchandising strategy and it empowers you to improve the search relevance manifolds. 

A customer might wish to find a 'baseball cap' when they search for 'Head Gear'. In this scenario, various synonyms that may apply can be managed by the synonyms dictionary that allows the customer to search and be presented with predefined synonym alternatives. 

For this you need to go to the synonym dictionary under search section and add keywords.

The following screenshot shows a sample of synonyms defined for a fashion store thus enhancing the reach of search relevance and reducing the chances of the dreaded zero search results.