antiparallelogram
... that an antiparallelogram is a crossed quadrilateral with two pairs of equal-length edges?
... that an <b id="mwAn8"><a href="./Antiparallelogram" id="mwAoA" rel="mw:WikiLink" title="Antiparallelogram">antiparallelogram</a></b> <i id="mwAoE">(example pictured)</i> is a <a href="./Quadrilateral#Complex_quadrilaterals" id="mwAoI" rel="mw:WikiLink" title="Quadrilateral">crossed quadrilateral</a> with two pairs of equal-length edges?