Source : Webster's Revised Unabridged Dictionary (1913)

Rectangle \Rec"tan`gle\ (r?k"t??`g'l), n. [F., fr. L. rectus
   right + angulus angle. See {Right}, and {Angle}.] (Geom.)
   A four-sided figure having only right angles; a right-angled
   parallelogram.

   Note: As the area of a rectangle is expressed by the product
         of its two dimensions, the term rectangle is sometimes
         used for product; as, the rectangle of a and b, that
         is, ab.

Rectangle \Rec"tan`gle\, a.
   Rectangular. [R.]

Source : WordNet®

rectangle
     n : a parallelogram with four right angles