A polygon with four sides.
An area defended by four fortresses supporting each other.
Having four sides.
A quadrilateral with two sides parallel.
The trapezium bone of the wrist.
A region on the ventral side of the brain, either just back of the pons Varolii, or, as in man, covered by the posterior extension of its transverse fibers.
A quadrilateral with two sides parallel and two sides non-parallel.