[tri.an.gle] n [ME, fr. L triangulum, fr. neut. of triangulus triangular, fr. tri- + angulus angle] (14c) 1: a polygon having three sides--compare spherical triangle
2. a: a percussion instrument consisting of a rod of steel bent into the form of a triangle open at one angle and sounded by striking with a small metal rod b: a drafting instrument consisting of a thin flat right-angled triangle of wood or plastic with acute angles of 45 degrees or of 30 degrees and 60 degrees
3: a situation in which one member of a couple is involved in a love affair with a third person