An oblique-angled parallelogram like a rhomb, but having only the opposite sides equal, the length and with being different.

quadangular, with the lateral angles obtuse.

quadrangular, with the lateral angles obtuse.

a parallelogram with adjacent sides of unequal lengths; an oblique-angled parallelogram with only the opposite sides equal

shaped like a rhombus or rhomboid; "rhomboidal shapes"

Greek rhombus = a figure with 4 equal sides, not at right angles, and eidos = shape or form, hence, the shape of a rhombus.

A rhomboid is a parallelogram with oblique angles and adjacent sides have different lengths.

The shape of a diamond in a pack of cards.