A general term indicating how well a site or page is currently performing in the search engines. It is often confused with PageRank. While PageRank is certainly important in determining a site’s Google ranking, there are many other factors that also affect the final result.
The idea of ranking by itself has little value, however. It is important also to specify the keyword for which the site is ranking. Ranking well for a highly competitive, high traffic term is obviously a very different thing than ranking for something for which no one will search.
Also bear in mind that rankings are highly personalised to each web user, based on their location, search history and other factors.