Source : Webster's Revised Unabridged Dictionary (1913)

Lithophyse \Lith"o*physe\, n. [Litho- + Gr. ? a flatus, air
   bubble.] (Min.)
   A spherulitic cavity often with concentric chambers, observed
   in some volcanic rocks, as in rhyolitic lavas. It is supposed
   to be produced by expanding gas, whence the name.