trapezium

A quadrilateral having no parallel sides.

A trapezoid.

A bone in the wrist at the base of the thumb.

In geometry: Any quadrilateral not a parallelogram. A trapezoid.

An irregular quadrangle in the nebula of Orion, formed by its four brightest stars.

In geometry, a plane figure contained by four straight lines of which no two are parallel.

In anatomy:

A cross-band of fibers near the lower border of the pons Varolii, passing from the region of the accessory auditory nucleus to the raphe.

The bone on the radial side of the distal row of carpal bones, articulating with the metacarpal bone of the thumb; carpale I. of the typical carpus, whatever its actual shape. Also called multangulum majus. See cuts under Perissodactyla, scapholunar, and hand.