hyperboloid

hyperboloid
    n 1: a quadric surface generated by rotating a hyperbola around
         its main axis
    

Hyperboloid \Hy*per"bo*loid\, a. (Geom.)
   Having some property that belongs to an hyperboloid or
   hyperbola.
   [1913 Webster]
    

Hyperboloid \Hy*per"bo*loid\, n. [Hyperbola + -oid: cf. F.
   hyperbolo["i]de.] (Geom.)
   A surface of the second order, which is cut by certain planes
   in hyperbolas; also, the solid, bounded in part by such a
   surface.
   [1913 Webster]

   {Hyperboloid of revolution}, an hyperboloid described by an
      hyperbola revolving about one of its axes. The surface has
      two separate sheets when the axis of revolution is the
      transverse axis, but only one when the axis of revolution
      is the conjugate axis of the hyperbola.
      [1913 Webster]