1. a flat shape with three straight sides and three angles
Usage: geometry
2. a musical instrument consisting of a metal bar bent into a triangular shape that is struck to produce a ringing sound
Usage: music
3. a situation involving three people or things, especially a romantic relationship involving three people

Examples

• The students learned to calculate the area of a triangle.
• She drew an equilateral triangle on the board.
• The percussionist played the triangle during the orchestra performance.
• The metal triangle rang clearly when struck with the beater.
• The love triangle created tension between the three friends.
• The political triangle between the three nations was complex.
• Each triangle has three vertices and three sides.