triangle (Noun) — A three-sided polygon.
triangle (Noun) — Something approximating the shape of a triangle. ex. "the coastline of Chile and Argentina and Brazil forms two legs of a triangle"
triangle (Noun) — Any of various triangular drafting instruments used to draw straight lines at specified angles.
triangle (Noun) — A percussion instrument consisting of a metal bar bent in the shape of an open triangle.
triangle (Noun) — A small northern constellation near Perseus between Andromeda and Aries.