trapezium

noun

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