This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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n. A four-sided plane figure with opposite sides parallel.

n. A convex quadrilateral in which each pair of opposite edges are parallel and of equal length.

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.

n. In geometry, a quadrilateral whose opposite sides are parallel.

n. A pantograph.

n. a quadrilateral whose opposite sides are both parallel and equal in length

"*This is reputed to be the first rock song to contain the word parallelogram in it."

parallelogram of forces    parallelogram of accelerations    parallelogram of momenta   

quadrangle    quadrilateral    tetragon   

complement of a parallelogram    parallelogram of velocities    parallelogram of accelerations    heronic parallelogram    parallelogram of forces    newton's parallelogram    rhombus    square   

rectangle    rhombus    rhomboid    diamond    rhomb   

parallelogram of forces   

trapezoid    rhombus    polygon    rectangle    pentagon    octahedral    equilateral    ellipse    zig-zagging    triangle