You used to be able to search on the Categories field of desktop files and search for "AudioVideo" or "Games" or "GTK"

This:

 A) Would require gmenu changes to bring back
 B) Doesn't integrate well with translation (we'd category translations)
 C) Can be inepxlicable at times

While long-term we probably do want to allow searching over keywords that aren't mutually exclusive, a short term thing to do is to just include the "menu" assigned by libgmenu (and displayed in Application Browse) into the search terms.