What are Google supplemental results?

[venkatjaya]

Supplemental Result is a URL residing in Google's supplemental index, a secondary database containing pages of less importance, as measured primarily by Google's PageRank algorithm.

 

[aarisseo]

Every time Google indexes a page, it checks to see if the page is already in its database. Duplicate content or pages which have not been accessed for a long time can then be labelled as a as a supplemental result.