n. In anthropology, a type of cranium with somewhat flattened vertex and basal region which are approximately in parallel planes.Having the shape of a trapezoid. See II., 1.n. In geometry, a plane four-sided figure having two of its opposite sides parallel, and the other two not so.n. In anatomy and zoology, the trapezoid bone, one of the bones of the wrist, so called from its shape; the second one of the distal row of carpal bones, on the radial or thumb side, between the trapezium and the magnum, in special relation with the head of the second metacarpal bone; carpale II. of the typical carpus. Also called multangulum minus, and trapezoides, trapezoideum. See cuts under Artiodactyla, pisiform, hand, and scapholunar.