Pl. -a, -ums. Also erron. 7–9 frustrum. [a. L. frustum piece broken off.]
1. Math. The portion of a regular solid left after cutting off the upper part by a plane parallel to the base; or the portion intercepted between two planes, either parallel or inclined to each other.
1658. Sir T. Browne, The Garden of Cyrus, iii. 57. Right lines and circles make out the bulk of plants; In the parts thereof we finde Helicall or spiral roundles, voluta’s, conicall Sections, circular Pyramids, and frustums of Archimedes.
1669. Phil. Trans., IV. 960. The Axis of a Pyramid, Cone, Sphere, Parabolical, and Hyperbolical Conoid, and of a Figure of different Bases, which he calls a Frustrum of a Prisme.
1706. W. Jones, Synopsis Palmariorum Matheseos, 265. The Curved Surfaces of Segments, or Frustrums of Spheres, cut by parallel Planes, are equal to the corresponding Surfaces of the Sphere’s Circumscr. Cylinder.
1779. Forrest, Voy. N. Guinea, 49. We could see within the straits a hill with a flat top, like what is called the frustum of a cone.
1812–6. Playfair, Nat. Phil., II. 291. This proposition is easily proved of pyramids, and frusta of pyramids, of which the solid angle is indefinitely small.
1828. J. M. Spearman, Brit. Gunner (ed. 2), 378. The difference between the two piles thus found will be the number in the frustum or incomplete pile.
1860. Maury, Phys. Geog. Sea, iv. § 218. We may … liken this belt of winds which encircles the earth … to the frustum of a hollow cone.
b. Applied to the sections of the shaft of a column.
1835. Willis, Pencillings (1836), II. xl. 23. We were directed to it by thirteen or fourteen frustra of enormous columns, which once formed the monument to his memory.
1850. Leitch, trans. Müllers Anc. Art, § 286. 316. A truncated pillar, or frustum of a column.
2. gen. A portion or fragment of anything material or immaterial, rare.
1721. Bailey, Frustum, a Fragment, a broken Piece.
a. 1733. R. North, Examen, III. viii. (1740), 624. This Frustum of a Libel is grafted into his pious History.
1812. Crabbe, T. in Verse, vii. Wks. 1834, IV. 288. She minced the sanguine flesh in frustrums fine.
1812. Knox & Jebb, Corr., II. 94. What I would deprecate is, putting into people’s hands the frusta of a system.
