\Pseu"do*sphere`\, n. [Pseudo- + sphere.] (Geom.)
The surface of constant negative curvature generated by the
revolution of a tractrix. This surface corresponds in
non-Euclidian space to the sphere in ordinary space. An
important property of the surface is that any figure drawn
upon it can be displaced in any way without tearing it or
altering in size any of its elements.