Parallelogram n. : A right-lined 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.

Example:
What is the difference between a Parallelogram and a trapezoid?

Taxonomy
parallelogram, sides, diagonals, area of a parallelogram, Fundamental parallelogram, Area of Parallelogram, free encyclopedia, quadrilateral, four sides, shape, vertices, parallel lines, area formula, right angles, rectangle, congruent triangles, measure, AE.

Defination from the web:
parallelogram is a quadrilateral with two sets of parallel sides. ... The three-dimensional counterpart of a parallelogram is a parallelepiped. ... The area of a parallelogram is twice the area of a triangle created by one of its diagonals. ...