Definition of "Triangle" :

noun: a percussion instrument consisting of a metal bar bent in the shape of an open triangle

noun: any of various triangular drafting instruments used to draw straight lines at specified angles

noun: a small northern constellation near Perseus between Andromeda and Aries

noun: a three-sided polygon

noun: something approximating the shape of a triangle

"The coastline of Chile and Argentina and Brazil forms two legs of a triangle."