from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The plane figure formed by connecting three points not in a straight line by straight line segments; a three-sided polygon.
- n. Something shaped like such a figure: a triangle of land.
- n. Any of various flat, three-sided drawing and drafting guides, used especially to draw straight lines at specific angles.
- n. Music A percussion instrument consisting of a piece of metal in the shape of a triangle open at one angle.
- n. A relationship involving three people, especially a ménage à trois.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A polygon with three sides and three angles.
- n. A percussion instrument made by forming a metal rod into a triangular shape which is open at one angle. It is suspended from a string and hit with a metal bar to make a resonant sound.
- n. A triangular shaped piece of equipment used for gathering the balls into the formation required by the game being played.
- n. A love triangle.
- n. The structure of systems composed with three interrelated objects.
from the GNU version of the Collaborative International Dictionary of English
- n. A figure bounded by three lines, and containing three angles.
- n. 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.
- n. A draughtsman's square in the form of a right-angled triangle.
- n. 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.
- n. A small constellation situated between Aries and Andromeda.
- n. A small constellation near the South Pole, containing three bright stars.
from The Century Dictionary and Cyclopedia
- n. A triangular box-fish, as Sectophrys trigonus, of the family Ostraciidæ of the West Indies.
- n. In angling, an arrangement of three fish-hooks bound together with the points outward, forming a triangle.
- Three-cornered; three-angled; triangular.
- n. In geometry, a figure composed of three lines which meet two by two in three points, called the vertiees of the triangle; especially, a rectilinear figure of this description.
- n. Any three-cornered or three-sided figure, body, or arrangement; anything having a triangular form or bounding a three-sided space.
- n. A musical instrument of percussion, made of a rod of polished steel bent into the form of a triangle, and open at one of its angles.
- n. [capitalized] In astron, same as Triangulum.
- n. Eccles., a symbol of the Trinity.
- n. A chest made in triangular form to hold a priest's cope.
- n. A three-cornered straight-edge, with one right angle and the other angles more or less acute, used in conjunction with the T-square for drawing parallel, perpendicular, or diagonal lines.
- n. A kind of gin for raising heavy weights, formed by three spars joined at top. See gin, 2 .
- n. Milit., formerly, in the British army, a sort of frame formed of three halberds stuck in the ground and united at the top, to which soldiers were bound to be flogged: generally in the plural.
- n. In ceramics, a form of the stilt consisting of three metal pins held together in the form of a triangle. See stilt, 5.
- n. One of certain tortricid moths: an English collectors' name. Tortrix rufana is the red triangle.
- n. In entomology, a large three-sided cell found in the wings of many dragon-flies.
- n. See conjugate triangles, under conjugate.
- n. A triangle whose sides are rectilinear.
- n. the circumscribed circle;
- n. the inscribed and the three escribed circles;
- n. the Feuerback or nine-point circle;
- n. the Brocard or seven-point circle;
- n. the Tucker or triplicate-ratio cirde;
- n. the sine triple-angle circle (constructed as follows: on the sides of the triangle ABC take D and D' on BC, E and E' on AC, F and F' on AB such that the angle AEF =AF'E' =A, BFD =BD'F' =B, CDE =CE'D' =C; then the circle in question passes through D, D', E, E', F, F', and DD': EE': FF'=sin 3A: sin 3B: sin 3C)
- n. the Taylor or six-point circle, which passes through the six feet of perpendiculars drawn to the sides from feet of perpendiculars on the sides from the vertices of the triangle
- n. the Spieker circle, or circle inscribed in the triangle whose vertices are the mid-points of the sides of the primitive triangle. See circle.
- n. the centroid, or intersection of median lines
- n. the orthocenter, or intersection of perpendiculars from the angles upon the opposite sides
- n. the circumcenter, or center of the circumscribed circle
- n. the center of the Feuerbach circle;
- n. the incenter, or center of the inscribed circle
- n. the radical center of the escribed circles;
- n. the symmedian, Grebe, or Lemoine point, the intersection of the three lines each bisecting a side and bisecting a perpendicular from an angle upon a side
- n. the Spieker point, or mid-point between the circumcenter and incenter
- n. the Brocard points, two points of the Brocard circle (which see, under circle) (through the symmedian point S of any triangle ABC lines are drawn parallel to the sides of the latter, meeting these sides in D and D' on BC, E and E' on AC, F and F' on AB, so that D, S. E' are collinear, as well as E, S, F' and F, S, D'; then the three lines through A parallel to FD, through B parallel to DE, and through C parallel to EF meet in one Brocard point P, while the lines through A parallel to D' E', through B parallel to E'F', and through C parallel to F' D' meet in the other Brocard point P')
- n. (10) the center of the triplicate-ratio circle; besides others.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. any of various triangular drafting instruments used to draw straight lines at specified angles
- n. a percussion instrument consisting of a metal bar bent in the shape of an open triangle
- n. something approximating the shape of a triangle
- n. a three-sided polygon
- n. a small northern constellation near Perseus between Andromeda and Aries
Middle English, from Old French, from Latin triangulum, from neuter of triangulus, three-angled : tri-, tri- + angulus, angle.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Old French triangle. (Wiktionary)