I see the term once in a while, but generally not in a rigorously defined context. And when I think in terms of the gravitational force per square meter on the Earth, for example, I'm not sure it's a concept I can grasp, since gravitational force is always defined with respect to a second body. If I write the mass of the earth, times the gravitational acceleration on the earth's surface, divided by the surface of the earth, I do get a force per square meter or pressure for the earth's surface, but it seems absurdly high, and I don't think that's a valid approach anyway. Any thoughts on this would be appreciated. Thanks.