I have heard of staggering intellect but does singular intellect mean the same? Which phrase should be used in what context?
According to https://www.merriam-webster.com/dictionary/singular, singular as an adjective can be defined as "distinguished by superiority" or "being out of the ordinary." Therefore, when singular is used to modify the word intellect, it means superior/extraordinary intellect. According to http://www.thesaurus.com/browse/staggering, a synonym for staggering is extraordinary. Therefore, these two things mean similar things as they both refer to a high intellectual level.