The inhabitants of each Material Plane always refer to their own plane as the Prime Material Plane.
In the cosmology shared by the Planescape and Spelljammer settings, there is only one Prime Material Plane, which contains many different worlds. In other cosmologes, such as that used by the Manual of the Planes, there are numerous different Material Planes. (The Third Edition Manual of the Planes refers exclusively to the "Material Plane" rather than the "Prime Material Plane".)
In the Planescape campaign setting, those persons coming to the extraplanar city of Sigil from the Prime are referred to as "primes" themselves. "Primes" are often treated as clueless inferiors by the planar elitists who dwell in Sigil and other planes.
In 4th Edition, the terms "Prime Material Plane" and "Material Plane" are no longer in use, the plane of existence on which adventures normally take place is simply known as the world.
Death in Knoxville.(Reading the World: Cormac McCarthy's Tennessee Period)(The Making of James Agee)(Book review)
Sep 22, 2011; Dianne C. Luce. Reading the World: Cormac McCarthy's Tennessee Period. Columbia: U of South Carolina P, 2009. xiii + 314 pages....