Quad eXtended Graphics Array
Quad eXtended Graphics Array, or QXGA, is a display standard that defines a resolution of 2048x1536. It is meant to be used with 4:3 displays. It's name comes from the fact that is has four times the resolution of XGA This is technically the highest resolution that is not considered experiemental (as of 2008), but it is not used with a wide range of displays. However, there are CRTs that will display QXGA that would definitely cost quite a lot less than counterparts advertised with the functionality.
The widescreen variant is WQXGA.