/ ˈtraɪæŋgl; NAmE / noun
1.
a flat shape with three straight sides and three angles; a thing in the shape of a triangle :
( BrE )
a right-angled triangle
( NAmE )
a right triangle
Cut the sandwiches into triangles.
2.
a simple musical instrument that consists of a long piece of metal bent into the shape of a triangle, that you hit with another piece of metal
3.
a situation involving three people in a complicated relationship :
a love triangle
—see also eternal triangle
4.
( NAmE ) = set square
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WORD ORIGIN
late Middle English : from Old French triangle or Latin triangulum , neuter of triangulus three-cornered (see tri- and the noun angle ).