define Clustering

Definition:

In search results the listings from any individual site are typically limited to a certain number and grouped together to make the search results appear neat and organized and to ensure diversity amongst the top ranked results. Clustering can also refer to a technique which allows search engines to group hubs and authorities on a specific topic together to further enhance their value by showing their relationships.

Clustering, on the other hand also helps searcher narrow down options to get a more precise area on the topic of search.