Quadrilateral means four-sided.(adjective)
An example of something quadrilateral is a square.
Quadrilateral is defined as a shape with four sides and four angles.(noun)
An example of a quadrilateral is a rectangle.
See quadrilateral in Webster's New World College Dictionary
Origin: < L quadrilaterus (see quadri- & lateral) + -al
See quadrilateral in American Heritage Dictionary 4
Learn more about quadrilateral