pa·rab·o·loid 
(pə-răbə-loid′)
(pə-răbə-loid′)n.
A surface having parabolic sections parallel to a single coordinate axis and elliptic or circular sections perpendicular to that axis.
pa·rab′o·loidal (-loidl) adj.
paraboloidThe equation for
a circular paraboloid is
x2/a2
+
y2/b2
= z.