Pronunciation: (trī'ang"gul),[key] —n. 1. a closed plane figure having three sides and three angles.
2. a flat triangular piece, usually of plastic, with straight edges, used in connection with a T square for drawing perpendicular lines, geometric figures, etc.
3. any three-cornered or three-sided figure, object, or piece: a triangle of land. 4. a musical percussion instrument that consists of a steel triangle, open at one corner, that is struck with a steel rod.
5. a group of three; triad.
6. a situation involving three persons, esp. one in which two of them are in love with the third.
7. (cap.) Astron.the constellation Triangulum.