Plain English Meaning
A VOR ground station that sits on the airport itself, so the approach is flown directly to or from the station rather than to a separate fix some distance away.
Full Definition
A VHF Omnidirectional Range navigation facility physically located on the airport grounds, used as the final approach fix or final approach navaid for a non-precision instrument approach to that same airport.
Context Anchor
Seen on instrument approach procedures and approach charts for VOR approaches.