n.  1.  (Geom.) A rightlined quadrilateral figure, whose opposite sides are parallel, and consequently equal;  sometimes restricted in popular usage to a rectangle, or quadrilateral figure which is longer than it is broad, and with right angles.

Noun  1.  parallelogram  a quadrilateral whose opposite sides are both parallel and equal in length Antonyms: trapezium  a quadrilateral with no parallel sides 