The Collaborative International Dictionary of English v.0.48:
Geostatic \Ge`o*stat"ic\, a. [Gr. ge`a, gh^, earth + E. static.] (Civil Engin.) Relating to the pressure exerted by earth or similar substance. [1913 Webster] Geostatic arch, an arch having a form adapted to sustain pressure similar to that exerted by earth. --Rankine. [1913 Webster]