what is partial ground plane

can any one explain me what is partial ground plane ..why we use partial ground plane ..can any one justify

Partial ground plane is an empirical way to define a ground which dimensions are smaller than should be.
There are different types of ground planes. Ground plane of a PCB or ground plane of an antenna.
http://en.wikipedia.org/wiki/Ground_plane

If it is related to PCB design then partial GND plane also called as split GND plane.
some times It is necessary to use power and GND in same plane in order to reduce number of layers required for PCB.