Trapezium
Trapezium, describing a geometric shape, has two contradictory meanings:
Outside the US and Canada: a quadrilateral with at least one pair of parallel sides (known in the US as a trapezoid)
In the US and Canada: a quadrilateral with no parallel sides (known elsewhere as a general irregular quadrilateral)

Trapezium can also mean:

Trapezium (bone), a bone in the wrist
Trapezium (astronomy), a group of stars in the Orion Nebula
Trapezium (play), by Henry Rathvon