<p><strong>Noun</strong></p><ul><li>A closed plane figure having three sides and three angles.</li><li>A flat triangular piece, usually of plastic, with straight edges, used in connection with a T-square for drawing perpendicular lines, geometric figures, etc.</li><li>Any three-cornered or three-sided figure, object, or piece: a triangle of land.</li><li>A musical percussion instrument that consists of a steel triangle, open at one corner, that is struck with a steel rod.</li><li>A group of three; triad.</li><li>A situation involving three persons, especially one in which two of them are in love with the third.</li><li>Triangle, Astronomy: the constellation Triangulum.</li></ul>