triangle UK /ˈtɹaɪəŋɡəl/US /ˈtɹaɪˌæŋɡəl/noun 10verb 1forms 3phrases 1 noun10 •A polygon with three sides and three angles.The wedge-shaped character was the triangle, the archaic Paleolithic sign of the vulva; the pubic triangle was at the end of the phallic stylus. — 1981 •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. •A love triangle.One of the writers' most pleasing inventions was to treat the triangle love story as comedy. — 2009 •The structure of systems composed with three interrelated objects. •(US, Canada) A set square. •A draughtsman's square in the form of a right-angled triangle. •A triangular piece of equipment used for gathering the balls into the formation required by the game being played. •A triangular formation of railway tracks, with a curve on at least one side.After turning on the triangle at Jeumont, we set off light engine back to Aulnoye. — 1961 •Any of various large papilionid butterflies of the genus Graphium. •[usually plural] (historical) A frame formed of three poles stuck in the ground and united at the top, to which people were bound for corporal punishment.I was flogged in 1840. To this day I feel a pain in the chest from the triangles. — 1851 verb1 •To form or be included in a three-part interaction, e.g., a Karpman drama triangle, such as by being ganged up on by two people or being torn between conflicting demands from two sources. formstriangled · triangling · triangles Phrases with triangle eternal triangleA relationship involving three persons (usually two women and one man or two men and one woman) among whom there are conflicting and competing attachments of a romantic or emotional nature.