noun Geometry.
a surface that can be put into a position such that its sections parallel to at least one coordinate plane are parabolas.

1650–60; parabol(a) + -oid

paraboloidal [puh-rab-uh-loid-l, par-uh-buh-] , adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
paraboloid (pəˈræbəˌlɔɪd)
a geometric surface whose sections parallel to two coordinate planes are parabolic and whose sections parallel to the third plane are either elliptical or hyperbolic. Equations x²/a² ± y²/b² = 2cz

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Science Dictionary
paraboloid   (pə-rāb'ə-loid')  Pronunciation Key 
A surface having parabolic sections parallel to a single coordinate axis and elliptic sections perpendicular to that axis.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica


an open surface generated by rotating a parabola (q.v.) about its axis. If the axis of the surface is the z axis and the vertex is at the origin, the intersections of the surface with planes parallel to the xz and yz planes are parabolas (see , top). The intersections of the surface with planes parallel to and above the xy plane are circles. The general equation for this type of paraboloid is x2/a2 + y2/b2 = z

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
The ideal concentrator shape is a paraboloid of revolution.
Both these factors the form of a frustum of a paraboloid, then the equations
  can affect displacement.
The density profile for a typical experimental condensate is thus an inverted
  paraboloid when the confining potential is harmonic.
The paraboloid shape is perfect for focusing the sunlight on the tube.
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