Trapezium

Noun

1. A quadrilateral with two sides parallel.
2. A quadrilateral with two sides parallel and two sides non-parallel.
3. A four-sided polygon with no parallel sides and no sides equal; a simple convex irregular quadrilateral.
4. The trapezium bone of the wrist.
5. 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.