[ trahy-ang-guhl ]
See synonyms for triangle on
  1. a closed plane figure having three sides and three angles.

  2. a flat triangular piece, usually of plastic, with straight edges, used in connection with a T square for drawing perpendicular lines, geometric figures, etc.

  1. any three-cornered or three-sided figure, object, or piece: a triangle of land.

  2. a musical percussion instrument that consists of a steel triangle, open at one corner, that is struck with a steel rod.

  3. a group of three; triad.

  4. a situation involving three persons, especially one in which two of them are in love with the third.

  5. Triangle, Astronomy. the constellation Triangulum.

Origin of triangle

First recorded in 1350–1400; Middle English, from Latin triangulum, noun use of neuter of triangulus “three-cornered”, see tri-, angle1

Other words from triangle

  • triangled, adjective

Words Nearby triangle Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use triangle in a sentence

British Dictionary definitions for triangle


/ (ˈtraɪˌæŋɡəl) /

  1. geometry a three-sided polygon that can be classified by angle, as in an acute triangle, or by side, as in an equilateral triangle. Sum of interior angles: 180°; area: 1/2 base × height

  2. any object shaped like a triangle

  1. any situation involving three parties or points of view: See also eternal triangle

  2. music a percussion instrument consisting of a sonorous metal bar bent into a triangular shape, beaten with a metal stick

  3. a group of three

Origin of triangle

C14: from Latin triangulum (noun), from triangulus (adjective), from tri- + angulus corner

Derived forms of triangle

  • triangled, adjective

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for triangle


[ trīăng′gəl ]

  1. A closed geometric figure consisting of three sides.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Other Idioms and Phrases with triangle


see eternal triangle.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.