ellipsoidThe equation for an ellipsoid is x2/a2 + y2/b2 + z2/c2 = 1.el·lip·soid (?-l?p?soid?)n. A geometric surface, all of whose plane sections are either ellipses or circles.el·lip?soid?, el·lip?soi?dal (?-l?p?soid?l, ?l??p-, ??l?p-) adj.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.ellipsoid (??l?ps??d) n (Mathematics) a. a geometric surface, symmetrical about the three coordinate axes, whose plane sections are ellipses or circles. Standard equation: x2/a2 + y2/b2 + z2/c2 = 1, where ±a, ±b, ±c are the intercepts on the x-, y-, and z- axesb. a solid having this shape: the earth is an ellipsoid. ellipsoidal adjCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014el?lip?soid (??l?p s??d) n. 1. a solid figure whose plane sections are all ellipses or circles. adj. 2. ellipsoidal. [1715?25;