pyramidoid Geom. rare.
(pɪˈræmɪdɔɪd)
[ad. mod.L. pȳramidoīdes (sc. schēma): see pyramid and -oid.]
A solid figure in form approaching a pyramid, but of which the edges that meet or intersect at the vertex are curves, instead of straight lines as in a pyramid; as the parabolic pyramidoid, in which the vertical sections through the edges are parabolas instead of triangles.
| [1655 J. Wallis De Sectionibus Conicis Prop. ix, De Conoide et Pyramidoide Parabolico. Ibid. xiv, De Elliptico Pyramidoide et Conoide. 1656 ― Arithmetica Infinitorum Prop. iv, Item, Pyramidoides vel Conoides Parabolicum..ad Prisma vel Cylindrum (super æquali base æquealtum) est ut 1 ad 2.] 1704 J. Harris Lex. Techn. I, Parabolick Pyramidoid..so named by Dr. Wallis from its Genesis, or Formation. 1795 Hutton Math. Dict. s.v. Parabola. |
¶ Erroneously identified with a parabolic spindle.
| 1710 J. Harris Lex. Techn. (ed. 2) II. s.v.; thence 1727 in Bailey vol. II, and 1730 folio; 1839 Encycl. Brit. XVIII. 746/2; and some recent Dicts. |
So pyramiˈdoidal a., (a) Of or pertaining to a pyramidoid. (b) Of the general figure of a pyramid upon a base of any shape.
| 1807 T. Young Nat. Philos. II. 20 All pyramidoidal solids are equal to one third of the circumscribing prismatic or cylindroidal solids of the same height. |