Webster
✕

Webster’s Revised Unabridged Dictionary · 1913

Triangle

Tri′an′gle (trī′ăn̲′g'l), n. [L. triangulum, fr. triangulus triangular; tri- (see Tri-) + angulus angle: cf. F. triangle. See Angle a corner.] 1. (Geom.) A figure bounded by three lines, and containing three angles.

☞ A triangle is either plane, spherical, or curvilinear, according as its sides are straight lines, or arcs of great circles of a sphere, or any curved lines whatever. A plane triangle is designated as scalene, isosceles, or equilateral, according as it has no two sides equal, two sides equal, or all sides equal; and also as right-angled, or oblique-angled, according as it has one right angle, or none; and oblique-angled triangle is either acute-angled, or obtuse-angled, according as all the angles are acute, or one of them obtuse. The terms scalene, isosceles, equilateral, right-angled, acute-angled, and obtuse-angled, are applied to spherical triangles in the same sense as to plane triangles.

2. (Mus.) An instrument of percussion, usually made of a rod of steel, bent into the form of a triangle, open at one angle, and sounded by being struck with a small metallic rod.

3. A draughtsman's square in the form of a right-angled triangle.

4. (Mus.) A kind of frame formed of three poles stuck in the ground and united at the top, to which soldiers were bound when undergoing corporal punishment, — now disused.

5. (Astron.) (a) A small constellation situated between Aries and Andromeda. (b) A small constellation near the South Pole, containing three bright stars.

Triangle spider (Zoöl.), a small American spider (Hyptiotes Americanus) of the family Ciniflonidæ, living among the dead branches of evergreen trees. It constructs a triangular web, or net, usually composed of four radii crossed by a double elastic fiber. The spider holds the thread at the apex of the web and stretches it tight, but lets go and springs the net when an insect comes in contact with it.

Webster’s Revised Unabridged Dictionary, Noah Porter, editor (Springfield, Mass.: G. & C. Merriam, 1913). Public domain. Text as transcribed by MICRA, Inc., from Project Gutenberg. Changed for Deep Dive Bible: Greek, which our source spelled in Latin letters, set in Greek letters; entries of one spelling merged into one article; Greek words our source left out (shown as “?”), read from the 1898 printing, from the same plates (the Library of Congress’s copy), where the place could be found with certainty. Of the others, 1,362 (a word or a single letter each) were inferred by AI from the context by the dictionary’s own rules and are marked with a wavy underline (tap or point at one to see the note); the rest, which could not be inferred with confidence, are left as “?”.