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.