Plain English Meaning
A radio signal sent out in every direction from a ground station, on a VHF frequency, that gives nearby aircraft the GPS correction data they need to fly a precise approach to the runway.
Full Definition
A ground-based radio transmission, broadcast on a VHF frequency in all directions, that sends Ground Based Augmentation System (GBAS) correction and approach data to aircraft. The VDB carries the differential GPS corrections and the approach path information that a GBAS-equipped aircraft uses to fly a precision approach.
Context Anchor
Seen in diagrams and explanations of ground-based satellite in training.