a four-sided figure in a circle, with each vertex (corner) of the quadrilateral touching the circumference of the circle
a quadrilateral for which a circle can be circumscribed so that it touches each polygon vertex
a quadrilateral that can be inscribed in a circle
a quadrilateral that has all four vertices on a circle
A quadrilateral circumscribed by a circle so that all its vertices lie on the circumference of the circle.
A quadrilateral inscribed in a circle (Lesson 7.4).
In geometry, a cyclic quadrilateral is a quadrilateral whose vertices all lie on a single circle. The vertices are said to be concyclic.