trapezoid

n. plane figure with four sides of which exactly two are parallel

A trapezoid (in North America) or trapezium (in Britain and elsewhere) is a quadrilateral, which is defined as a shape with four sides, which has one set of parallel sides. Some authors define it as a quadrilateral having exactly one set of parallel sides, so as to exclude parallelograms. The exactly opposite kind of quadrilateral, that is, one which does not have any parallel sides, is called a trapezium in North America and a trapezoid in Britain and elsewhere. This article uses the North American wording. It also admits parallelograms as special cases of trapezoids (however, in this case, it is assumed that one set of parallel sides is distinguished, and is the one referred to as "the set of parallel sides").
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Trapezoid /trap·e·zoid/ 1. having the shape of a four-sided plane, with two sides parallel and two diverging. 2. [more]Trapezoid - Community and Resources

Noun
1. a quadrilateral with two parallel sides
(hypernym) quadrilateral, quadrangle, tetragon
(classification) United States, United States of America, America, US, U.S., USA, U.S.A.
2. the wrist bone between the trapezium and the capitate bones
(synonym) trapezoid bone, os trapezoideum
(hypernym) carpal bone, carpal, wrist bone

n. trapezoid, plane figure with four sides of which exactly two are parallel