from
The Collaborative International Dictionary of English v.0.48
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]