Definitions for "Relevance ranking"
the act of displaying the results of a search in the order of their relevance to the search terms
listing retrieved items in a order based on the system's computation of how closely documents correspond to the user's information need. Thus the first item is that which the system determines corresponds most closely.
the order in which Altavista displays the documents found. The most relevant ones will be shown first, that is the ones where the keywords searched are repeated more often