I have heard this word a million times, still dont know what it means.
As far as I know, it is a software program for FS that allows you to edit scenery and 'goings on' in FS.
Lee Sword (Author of AFCAD v1.4.0) wrote:
This is a CAD-style editor for airport facility data. You can create new parking, modify taxiways, add ATC to airports that don't already have it, create new airport facilities from scratch, and other things. It can't change the visual elements of an airport, just the maps and data that AI and ATC use to operate at airports, and the information that appears in you Map View and GPS windows.
Theres the link for it