Definition of "trapezium"

(geometry, Britain, Australia, New Zealand) A quadrilateral with two sides parallel.

1. (restrictively) A quadrilateral with two sides parallel and two sides non-parallel.  examples

(geometry, US, dated) A four-sided polygon with no parallel sides and no sides equal; a simple convex irregular quadrilateral.  examples

(anatomy) The trapezium bone of the wrist.  examples

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.  examples