triangle

The plane figure formed by connecting three points not in a straight line by straight line segments; a three-sided polygon.

Something shaped like such a figure.

Any of various flat, three-sided drawing and drafting guides, used especially to draw straight lines at specific angles.

A percussion instrument consisting of a piece of metal in the shape of a triangle open at one angle.

A relationship involving three people, especially a ménage à trois.

A triangular box-fish, as Sectophrys trigonus, of the family Ostraciidæ of the West Indies.

In angling, an arrangement of three fish-hooks bound together with the points outward, forming a triangle.

Three-cornered; three-angled; triangular.

In geometry, a figure composed of three lines which meet two by two in three points, called the vertiees of the triangle; especially, a rectilinear figure of this description.