trapezium

noun5

1. •
   (UK, Australia) A quadrilateral with two sides parallel.
2. •
   (UK, Australia) A quadrilateral with two sides parallel and two sides non-parallel.
3. •
   The trapezium bone of the wrist.
4. •
   (US, old-fashioned) A four-sided polygon with no parallel sides and no sides equal; a simple convex irregular quadrilateral.
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.