Source : Webster's Revised Unabridged Dictionary (1913)

Rectangular \Rec*tan"gu*lar\ (r?k*t?n"g?*l?r), a. [CF. F.
   rectangulaire.]
   Right-angled; having one or more angles of ninety degrees. --
   {Rec*tan"gu*lar*ly} (r?k*t?n"g?*l?r*l?), adv. --
   {Rec*tan"gu*lar*ness}, n.

Source : WordNet®

rectangular
     adj 1: having four right angles; "a rectangular figure twice as
            long as it is wide"
     2: having a set of mutually perpendicular axes; meeting at
        right angles; "wind and sea may displace the ship's center
        of gravity along three orthogonal axes"; "a rectangular
        Cartesian coordinate system" [syn: {orthogonal}]