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English definition of “triangle”

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triangle

noun [C] uk   /ˈtraɪ.æŋ.ɡl̩/ us  
B2 a flat shape with three straight sides: an equilateral/isosceles triangle anything that has three straight sides: Which earrings did you buy in the end - the triangles or the circles? a musical instrument consisting of a thin metal bar bent into a triangle shape that is hit with a metal bar to make a sound US ( UK set square) a flat piece of metal or plastic in the shape of a triangle with one angle of 90°, used for drawing angles ( also frame) a three-sided frame for arranging the balls at the start of a game of billiards , pool, etc.
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(Definition of triangle from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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