ELLIPSOID
ellipsoid, ellipsoidal, spheroidal
(adjective) having the nature or shape of an ellipsoid
ellipsoid
(noun) a surface whose plane sections are all ellipses or circles; “the Earth is an ellipsoid”
Source: WordNet® 3.1
Etymology
Noun
ellipsoid (plural ellipsoids)
(mathematics, geometry) A surface, all of whose cross sections are elliptic or circular (including the sphere), that generalises the ellipse and in Cartesian coordinates (x, y, z) is a quadric with equation x2/a2 + y2/b2 + z2/c2 = 0.
(geography) Such a surface used as a model of the shape of the earth.
Usage notes
The general case, with semiaxes a, b and c all different, is a triaxial ellipsoid (more rarely, scalene ellipsoid). If two are the same, say b = c, the result is an ellipsoid of revolution, which may be oblate (if a < b) or prolate (a > b). The degenerate case a = b = c is a sphere. An ellipsoid of revolution is also called a spheroid.
Hypernyms
• quadric surface, quadric
Adjective
ellipsoid (comparative more ellipsoid, superlative most ellipsoid)
Shaped like an ellipse; elliptical.
(mathematics) Of or pertaining to an ellipse; elliptic.
(botany) Having the tridimensional shape of an ellipse rotated on its long axis.
Source: Wiktionary
El*lip"soid, n. Etym: [Ellipse + -oid: cf. F. ellipsoide.] (Geom.)
Definition: A solid, all plane sections of which are ellipses or circles.
See Conoid, n., 2 (a).
Note: The ellipsoid has three principal plane sections, a, b, and c,
each at right angles to the other two, and each dividing the solid
into two equal and symmetrical parts. The lines of meeting of these
principal sections are the axes, or principal diameters of the
ellipsoid. The point where the three planes meet is the center.
Ellipsoid of revolution, a spheroid; a solid figure generated by the
revolution of an ellipse about one of its axes. It is called a
prolate spheroid, or prolatum, when the ellipse is revolved about the
major axis, and an oblate spheroid, or oblatum, when it is revolved
about the minor axis.
El*lip"soid, El`lip*soi"dal, a.
Definition: Pertaining to, or shaped like, an ellipsoid; as, ellipsoid or
ellipsoidal form.
Source: Webster’s Unabridged Dictionary 1913 Edition